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Excessive lead burden among golden eagles in the Swiss Alps

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2015 Environ Res Lett 10 034003

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Environ Res Lett 10 (2015) 034003 doi1010881748-9326103034003

LETTER

Excessive lead burden among golden eagles in the Swiss Alps

MilenaMMadry1 ThomasKraemer1 JacquelineKupper2 HanspeterNaegeli2 Hannes Jenny3Lukas Jenni4 andDavid Jenny4

1 Zurich Institute of ForensicMedicine Department of Forensic Pharmacology andToxicology University of Zurich Switzerland2 Institute of Veterinary Pharmacology andToxicology University of Zurich-Vetsuisse Switzerland3 Fish andGameDepartment of the Canton ofGrisons Chur Switzerland4 SwissOrnithological Institute Sempach Switzerland

E-mail lukasjennivogelwartech

Keywords lead toxicity golden eagle eagle owl lead ammunition lead isotopes

Supplementarymaterial for this article is available online

AbstractFragments from lead ammunition pose a poisoning risk for predators like golden eagles that scavengeon non-retrieved carcasses or offal left behind by hunters Three golden eagles were found in the SwissAlpswith an acute lead poisoning To investigate whether the few cases of lead-poisoned golden eaglesare exceptional events orwhether a substantial proportion of the Alpine golden eagle population isaffected by lead at sublethal levels wemeasured body burdens in golden eagles fromSwitzerland incomparison to eagle owls from the same area and to their respective prey These two raptor speciesdiffer in their food as eagle owls feed on live-caught prey Lead levels in soft tissues were significantlyhigher in golden eagles (median 114 μg gminus1 dryweight in liver 099 μg gminus1 in kidney) than in eagleowls (014 and 023 μg gminus1) Bones of golden eagles contained 10 timesmore lead (median of1245 μg gminus1 dryweight) than owl bones (128 μg gminus1) which represent substantially higher levels thanpreviously reported for golden eagles Bones of prey of both golden eagles and eagle owls had low leadconcentrations In order to investigate whether the sublethal lead of golden eagles originates fromammunition or from generic environmental contamination we examined lead isotope ratios Leadisotope signatures of golden eagle boneswere very similar to those of ammunition but differed fromthe signatures of bones of their prey eagle owls and soil Isotope signatures did not changewithincreasing bone lead concentration in golden eagles or any other group examined Thesefindingsindicate that in theAlpsmost golden eagles take up lead from spent ammunition in carcasses or theiroffal in sublethal quantities throughout their life and a few in lethal quantities leading to acute leadpoisoning

1 Introduction

Poisoning by lead is recognized as a major threat toscavenging raptors and lead intake is still the mostcommon toxic hazard occurring in raptors worldwide(Wayland et al 1999 Harmata and Restani 2013 Haiget al 2014) Lead poisoning is a special challenge tolarge predatory birds because their reproduction andmortality are naturally low and therefore the loss of afew individuals can seriously affect the survival of apopulation or even a species (Carpenter et al 2003Finkelstein et al 2010 Lambertucci et al 2011) Themajor source of lead in terrestrially foraging raptor

species was identified to be the ingestion of ammuni-tion fragments embedded in wounded prey animals ornon-removed carcasses or their offal which can lead toacute lead poisoning (Carpenter et al 2003 Churchet al 2006 Fisher et al 2006 Martin et al 2008 StansleyandMurphy 2011)

Acute lead poisoning is also known from goldeneagles (Aquila chrysaetos) in North America (Craiget al 1990 Kramer and Redig 1997 Waylandet al 1999) the UK (Pain et al 1995) Sweden (Kendallet al 1996) and Spain (Cerradelo et al 1992) In theAlps a few cases of lead-poisoned golden eagles arereported from Austria Switzerland and Germany

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(Bezzel and Fuumlnfstuumlck 1995 Zechner et al 2005Kenntner et al 2007) and we add another three casesin this study In all cases ingestion of spent leadammunition was suspected or found to be the reasonfor acute poisoning

The question however remains whether these fewcases of acutely lead-poisoned golden eagles in theAlps are exceptional events or whether they representthe lsquotip of the icebergrsquo of a substantial proportion ofthe Alpine golden eagle population affected by lead atsublethal levels If so a follow-up question is whetherthe sublethal lead of golden eagles originates fromammunition or from generic environmental con-tamination In contrast to acute lead-poisoning sub-lethal levels of lead in birds are much less well known(Haig et al 2014) Sublethal chronic lead assimilationmay result in higher mortality or reduced reproduc-tion (Pain et al 2009) potentially affecting a muchhigher proportion of the population than evidencedfrom individuals found with symptoms of acute leadpoisoning

In this study we first explored the level of leadcontamination in golden eagles of the Alps by per-forming a survey in birds found dead across easternSwitzerland Second we evaluated the sources of leadin these golden eagles In the Alps there are basicallytwo possible sources of lead a generic environmentalcontamination and consequent accumulation of thetoxic heavy metal along the food chain or the inges-tion of lead from ammunition used for upland hunt-ing To distinguish between these two possible sourcesof the toxicant we used three approaches

First we compared the lead concentrations in tis-sues and bones of golden eagles with those of eagleowls The rational basis of this side-by-side compar-ison between two predatory birds was that goldeneagles as frequent scavengers are more exposed tolead shot and fragments contained in non-retrievedcarcasses or offal than eagle owls which feed almostexclusively on live birds and small mammals killedwith their powerful talons

Second we analysed the concentration of lead inbones of prey animals captured by golden eagle andeagle owl to see whether a distinct lead concentrationin the two predators can be explained by different leadconcentrations in their prey

Third we compared lead isotope ratios betweensoil prey animals golden eagles eagle owls andammunition Isotope ratios have been shown to differbetween ammunition and other sources and thus havebeen used to distinguish between different sources oflead (Finkelstein et al 2010Walker et al 2013)

Our findings support the view that ammunitionused for hunting upland game is not only a cause ofmortality among scavenging birds of prey populationsin Switzerland but has lead to a substantial sublethalcontaminationwith yet unknown consequences

2Material andmethods

21 Sample collectionIn this study we used all golden eagles and eagle owlswe could get hold of mostly through the Fish andGame Department of the Canton of Grisons The 36golden eagles were found dead injured or moribundbetween 2006 and 2013 Most eagles were located inthe Canton of Grisons (N= 27) and additional indivi-duals in the Cantons of Berne (N= 3) Lucerne(N= 2) Glarus (N= 2) and Sankt Gallen (N= 2)From 31 of those liver kidney or bone samples wereobtained from 5 moribund only blood samples(supplementary data table S1 available at stacksioporgERL10034003mmedia) The 19 eagle owls werefrom the Canton of Grisons except two eagle owlsfound in the Cantons of Zurich and Glarus Mostgolden eagles were casualties of fatal intraspecificfights the majority of owls died of electrocution onpower lines or traffic The age of the birds wasdetermined from the stage of wing feathermoult Alsothe animals were x-rayed to exclude that they wereshot or had ingested bullet fragments Blood was takenfrom six living golden eagles one of which died Liverkidney and bones were collected from dead animalsand all samples were stored atminus20 degC

We sampled bones of animals preyed by goldeneagles (N= 10 mostly marmots Marmota marmota)and eagle owls (N= 16 birds rodents snow hares)which we found in or below their nests hence theywere not hunted (supplementary data table S2) Wealso sampled bones of 20 Alpine ibexes (Capra ibex)found dead in thewild hence not hunted (supplemen-tary data table S2) because golden eagles frequentlyfeed on their carcasses but their bones are rarelyfound in the nest and because ibexes are also hunted

Soil samples (N= 20) were taken from archivedsamples of the Cantonal (Department for Nature andEnvironment of the Canton of Grisons) and the SwissNational Soil Monitoring Network (NABO) (Meuliet al 2014) distributed over the whole area of the Can-ton of Grisons (supplementary data table S3) Threesamples were from sediments of a lake contaminatedby a historic abandoned oremine

In addition we analysed the composition of leadisotopes in 16 shot pellets and bullets two of themwere retrieved from a dead golden eagle and a beardedvulture respectively and 14 were from ammunitioncommonly used in the study area for hunting uplandgame (supplementary data table S4)

22 Sample digestion and extractionBlood samples were thawed and diluted with deio-nized water in a ratio of 110 for direct analysis Afterthawing the liver and kidney tissues were dried at100 degC to constant weight and on average 150 mg wasanalysed in duplicates From bones (humerus femursternum) adherent tissue was removed with a stainless

2

Environ Res Lett 10 (2015) 034003 MMMadry et al

steel scalpel the bones dried in an oven for 4 h toconstant weight and on average 250 mg was analysedin duplicates A previous study (Ethier et al 2007)demonstrated that these and other bones accumulatelead to the same levels

The tissue bone soil and ammunition sampleswere digested in closed Teflonreg vessels using 4 mL of65 (vv) nitric acid (SuprapurMerck) and 05 mL of30 (vv) hydrogen peroxide (Suprapur Merck)Digestion was carried out in a Microwave System(UltraCLAVE Milestone) with the heating programoperating in three steps (1) t= 0ndash10 min temperature(T) increase to 220 degC (2) t= 10ndash14 min T increasefrom 220 to 250 degC (3) t= 14ndash24 min T at 250 degCPressure and energy were 160 bars and 1000Wrespectively throughout the run These treatments athigh temperature were followed by cooling for 75 minDue to incomplete digestion of soil these sampleswere centrifuged (10 min at 4000 rpm) and decantedfrom silicate residues All samples were transferred toplastic flasks and filled up to 50 mL with water fol-lowed by a dilution at a ratio of 15 OnemL of the finalsolutionwas used for analyses

23Mass spectrometryLead concentrations were determined using an induc-tively coupled plasma mass spectrometer (ICP-MS)from Varian (Darmstadt Germany) Calibrationcurves were prepared in aqueous solutions using ICPMulti Element Standard Solution XXI CertiPur(Merck) For quantifications the average of leadisotopes 206Pb 207Pb and 208Pb was used Twodifferent positive control samples served to verify theaccuracy of the measurements Human Hair CertifiedReference Material No 13 (National Institute forEnvironmental Studies Japan) with a certified leadconcentration of 46 plusmn 06 μg gminus1 and Seronormtrade

Trace ElementsWhole Blood at lead concentrations of148 plusmn 10 and 336 plusmn 36 μg Lminus1 Negative control sam-ples were prepared in the samemanner as each samplebut without biological material The limit of quantifi-cation for lead was 01 μg Lminus1 Lead concentrations areexpressed on a dryweight basis except for blood

24Data analysisFor the comparison of bone lead concentrations ofgolden eagles eagle owls and their prey we ln-transformed the values and used a Bayesian hierarch-ical version of the one-way ANOVA in order to copewith unequal variances and multiple comparisonsPosterior distributions of the group means wereobtained by Monte-Carlo simulations using the pack-age sim from the R-package arm (R Core Team 2014Gelman and Hill 2007) Pairwise comparison betweengroups was done by calculating the posterior prob-ability of the hypothesis that the difference betweenmeans is larger than zero

Two isotope ratios were analysed statisticallybecause the third ratio is the product of the first twothus does not contain any further information Todescribe differences in the mean lead-ratios betweenthe seven groups we used a multivariate analysis ofvariance (MANOVA) with a bi-variate outcome vari-able Because the variance in the measurements dif-fered strongly between the different groups weestimated different residual variances for each groupTherefore we used a BayesianMANOVAwith hetero-geneity of variances in OpenBUGS (Spiegelhalteret al 2007) with weakly informative priors (accordingto Gelman et al 2014) The two-dimensional posteriordistribution of the mean lead isotope ratios for eachgroupwas described by 10 000 sampled pairs of valuesFrom these values we extracted the 95 confidenceellipses as two-dimensional credible intervals

3 Results

Three golden eagles were found with signs of acutelead poisoning They displayed high lead concentra-tions in the liver (774 μg gminus1) kidney (309 μg gminus1) orblood (563 and 1080 μg gminus1) (table 1)

The comparison between systematically collecteddead birds of the two raptor species (excluding thosewith acute intoxication signs reported in table 1)demonstrated that golden eagles displayed sig-nificantly higher lead concentrations than eagle owlsin liver (figure 1(A)) kidney (figure 1(B)) and bonetissue (figure 1(C)) The lead content in the liver of

Table 1 Lead concentrations in lead-poisoned golden eagles and corresponding normal reference values from the literature (ND notdetermined)

Liver (μg gminus1 dry weight) Kidney (μg gminus1 dryweight) Blood (μg dLminus1)

Bird Measured Referencesa Measured Referencesa Measured Referencesb

GR7 7735 lt6 (gt30when poisoned) 3088 lt6 (gt20when poisoned) ND lt20 (gt50when poisoned)

LU2 ND ND 5629

SG1 ND ND 1080

a Liver and kidney lead levels in golden eagles lt6 μg gminus1 dryweight indicate exposure to background lead concentrations levels gt6 μg gminus1 are

considered elevated levels gt30 μg gminus1 in the liver and gt20 μg gminus1in the kidney occur during lethal poisonings (Wayland et al 1999 Clark and

Scheuhammer 2003)b Blood concentrations lt20 μg dLminus1 are considered normal levels gt50 μg dLminus1 occur during poisoning (Franson et al 1983 Garcia-

Fernandez et al 1997 Pattee et al 2006 Stansley andMurphy 2011Harmata andRestani 2013)

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Environ Res Lett 10 (2015) 034003 MMMadry et al

Figure 1 Frequency distribution of lead concentrations in the liver (A) kidney (B) and bones (C) of golden eagles and eagle owlsNote the logarithmic y-axis Dotted lines indicate literature thresholds of elevated levels (6 μg gminus1 for liver and kidney 675 μg gminus1 forbones) see table 1 and text Lead concentration in liver kidney and bones all differ significantly between the two species (non-parametricMannndashWhitneyU-test plt0001) In addition the high value for liver and kidney from table 1 is also shown

4

Environ Res Lett 10 (2015) 034003 MMMadry et al

golden eagles ranged from 02 to 841 μg gminus1 with amedian value of 114 μg gminus1 (N= 25) The respectiveconcentrations in eagle owls ranged from 005 to041 μg gminus1 with amedian of only 014 μg gminus1 (N= 15)The lead content in the kidney of golden eagles rangedfrom 018 to 332 μg gminus1 with a median value of099 μg gminus1 (N= 24) The respective concentrations ineagle owls ranged from 010 to 099 μg gminus1 with amed-ian of only 023 μg gminus1 (N= 15) The largest differencebetween the two predatory bird species was detectedupon analysis of their bones In golden eagles the leadcontent in this mineralized tissue ranged from 122 to3840 μg gminus1 (median concentration 1245 μg gminus1N= 17) whereas in eagle owls the lead content of thebones ranged from 046 to 229 μg gminus1 (median con-centration 128 μg gminus1 N= 13) Only the lowestgolden eagle value was within the range of eagle owlvalues

Lead incorporated in the bones is thought to inte-grate all episodes of exposure within the life of an indi-vidual Therefore due to the continued accumulationof this heavymetal inmineralized tissues the lead con-tent of bones is expected to steadily increase with age(Rodriguez-Ramos Fernandez et al 2011) Howeveramong the golden eagles we observed an inverse trendof lead concentrations in the bones as the animals pro-gress from juvenile and sub-adult periods of life (lt5years old) to the adult stage (⩾5 years old figure 2) Inparticular the younger birds could be clearly sepa-rated in a group with low lead concentrations in thebones and another group with increased lead burden(gt25 μg gminus1) This pattern of lead accumulation may

indicate that young golden eagles with lead contents inbone exceeding 25 μg gminus1 may suffer from increasedmortality This view is confirmed by the observationthat the expected age-dependent increase of lead con-centrations in the bones is re-established when thebirds with values gt25 μg gminus1 are omitted from the cal-culations (figure 2)

The concentration of lead in bones of prey animalsfound in golden eagle and eagle owl nests (mean plusmn SD256 μg gminus1 plusmn 135 for golden eagle prey and295 μg gminus1 plusmn 063 for eagle owl prey) was indis-tinguishable from that of eagle owl bones but sig-nificantly lower than the values of golden eagle bones(figure 3) Lead concentration in bones of Alpineibexes was significantly lower than in prey animals oreagle owls (figure 3) There was no significant correla-tion between lead concentration in bones and the ageof Alpine ibexes (p= 086 linear regression)

The isotope ratios of 207Pb208Pb and 206Pb208Pbfound in the bones of golden eagles were statisticallyindistinguishable from those determined for ammuni-tion (figure 4) The isotope ratios in bones of prey ani-mals of the golden eagle ibexes eagle owls and in soilsamples were significantly different from the lead iso-tope ratios of both golden eagles and ammunition(figure 4) Prey animals of eagle owls were inter-mediate and statistically indistinguishable in their Pbisotope ratios from ammunition golden eagles andeagle owl bones In detail the isotope ratios in bones ofAlpine ibexes and of golden eagle prey animals aresimilar among each other Eagle owl bones showed alarge variation in both Pb isotope ratios and were sta-tistically different from bones of golden eagle preyibexes and golden eagles and from ammunition Soilsamples showed a very small variation in Pb isotoperatios and differed significantly from ammunitionand bones of golden eagles golden eagle prey eagleowl prey (figure 4)

There was no correlation between the lead isotoperatios and the lead concentration in bones of goldeneagles (p= 027 for 207Pb208Pb and p= 034 for206Pb208Pb linear regression) or in bones of eagleowls their prey Alpine ibex (taken together or sepa-rately) or soil samples (pgt 012 in all analyses linearregression) In particular the three soil samples fromsediments of a lake contaminated by the abandonedore mine showed very high lead concentrations(118ndash503 μg gminus1) but their isotope ratios did not dif-fer from the other soil samples (supplementary datatable S3)

4Discussion

In this study we found three cases of golden eagles inthe Alps with acute signs of lead poisoning confirmedby excessive concentrations of lead in blood liver andkidney (table 1) Once absorbed in the small intestinelead binds to red blood cells before being redistributed

Figure 2Bone lead concentrations of immature and subadult(lt5 years old) versus adult (⩾5 years old) golden eagles If thevalues gt25 μg gminus1 are omitted adult birds have significantlyhigher bone lead concentrations (958ndash3223 μg gminus1median1264 μg gminus1N= 9) than the immature and subadult animals(122ndash704 μg gminus1median 468 μg gminus1N= 4 non-para-metricMannndashWhitneyU-test p= 0007)

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Environ Res Lett 10 (2015) 034003 MMMadry et al

to highly perfused organs First there is a rapidexchange between the circulating blood and theparenchyma of liver kidney and the brain (Namet al 2012) By replacement of calcium ions this heavymetal is then slowly transferred into the bones whichultimately contain gt90 of the overall body burdenWhereas lead in liver and kidney has a turnover rate ofweeks to months bones constitute a long-term depot(Ethier et al 2007 Rodriguez-Ramos Fernandezet al 2011) As a consequence lead levels in blood aremeasured for the diagnosis of poisoning in living birdswhereas analyses of liver and kidney are used for thepost-mortem confirmation (see table 1)

The concentrations of lead in the bones of raptorsare usually not directly related to current episodes ofexposure (Ethier et al 2007 Gangoso et al 2009) butcan increase rapidly after lead ingestion (Sandersonand Bellrose 1986) Concentrations gt10 μg gminus1 in

bone tissue are considered to be elevated and con-centrations gt20 μg gminus1 are often observed after lethalpoisoning (Mateo et al 2003 Rodriguez-Ramos Fer-nandez et al 2011) Interestingly the lead concentra-tions in the bones of golden eagles found in our study(median of 1245 μg gminus1 dry weight) were substantiallyhigher than those previously reported in the literaturefor the same species For example Mateo et al (2003)detected bone concentrations between 049 and497 μg gminus1 dry weight in golden eagles found in SpainWayland et al (1999) divided the birds into those withbackground hepatic lead levels (lt6 μg gminus1) and thosewith elevated hepatic levels (gt6 μg gminus1) Mean bonelead concentrations in this Canadian study were41 μg gminus1 for the former group and 97 μg gminus1 for thelatter Clark and Scheuhammer (2003) found inCanada that 5 out of 9 birds had bone lead concentra-tions gt675 μg gminus1 whereas we found in our study a

Figure 3Mean bone lead concentration of golden eagles and eagle owls comparedwith their prey Lines are 95 confidence intervals(if not shown they are smaller than the symbol)Means not sharing the same symbol are significantly different from each other at theplt 0001 level Numbers in parentheses are sample sizes

Figure 4Mean ratio of 207Pb208Pb and 206Pb208Pb found in bones of golden eagles eagle owls their prey and inAlpine ibex as wellas in ammunition and soil Ellipses are 95 confidence intervals A sample is significantly different from another sample if themean isnot includedwithin the 95 confidence ellipse of the other sample

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Environ Res Lett 10 (2015) 034003 MMMadry et al

higher proportion (14 out of 17 specimens) with con-centrations in the bone gt675 μg gminus1

Other scavenging raptors are also likely to take uplead (see Rodriguez-Ramos Fernandez et al 2011)Among four examined bearded vultures from theAlps only one had a low lead concentration in bones(650 μg gminus1) while three had very high values(3890ndash10004 μg gminus1 Bassi et al (2013) Bassi et al inpress own unpublished data) Hence the bone leadconcentrations found in systematically collected deadgolden eagles in the eastern Swiss Alps was exception-ally high compared to those found in other goldeneagle populations In liver and kidney lead concentra-tions of golden eagles without signs of lead intoxica-tion did not exceed literature thresholds of elevatedlevels but were significantly higher than in eagle owlsHence although no signs of acute poisoning wereapparent even kidney and liver levels were elevatedcompared to another predator bird

Lead concentrations in bones of golden eagle preyanimals were gt10-fold lower than in golden eaglebones and ibex bones contained even gt20-fold lesslead (the median of 047 μg gminus1 found in this studycompares well with themedian of 059 μg gminus1 found byTataruch and Onderscheka (1995) in the same area)In contrast bones of eagle owl prey contained evenslightly more lead than eagle owl bones Therefore thelarge difference in bone lead concentration betweenthe two predators cannot be explained by differencesin lead concentration of their prey Part of the differ-ence between golden eagles and eagle owls in bone leadconcentration may be due to the fact that gastricpH values of owls are not quite as low as in raptors(Fisher et al 2006 Rodriguez-Ramos Fernandezet al 2011) and that owls regurgitate bones while rap-tors partly digest and partly regurgitate bones Hencethe absorption of ingested lead may be more completein raptors than in owls

The examination of lead isotope ratios revealedthat lead of golden eagles was most similar to that ofammunition used in the study area and differed fromthe isotope signature of golden eagle prey and soilsamples (even those with high lead concentrationsfrom ore mines or natural occurrence) Surprisinglythere was no change in isotope signature with increas-ing lead concentration in bones of golden eagles (orany other sample) This indicates that the source oflead ie from ammunition remains the same irre-spective of the amount of lead up-take

Taken together our findings indicate that lead ingolden eagles originates from ammunition and is notthe consequence of a bioaccumulation of genericallyavailable lead in the environment (eg from old oremine or aerial deposition of industrial lead) The find-ing that lead is accumulated in very high amounts inbones of golden eagles and is present in higheramounts than in another predator species even inliver and kidney suggests a frequent uptake of sub-lethal amounts of lead The lead concentration in

segments of wing feathers showed an irregular patternindicating an episodic rather than continuous leaduptake (ownunpublished data)

There are two main sources of ammunition leadfor golden eagles in the Alps which cannot be dis-tinguished by this study First golden eagles could feedon animals shot with lead pellets which were notretrieved or whose carcasses were left in the environ-ment (eg fox carcasses after skinning) Secondgolden eagles could take up lead fragments from ani-mals or their offal shot with lead bullets still themainammunition of hunters in the study area

When striking their targets conventional lead-based rifle bullets partly disintegrate intometallic frag-ments causing a widespread contamination of animaltissues (Church et al 2006 Hunt et al 2006 Bassi andFerloni 2012 Trinogga et al 2013 Haig et al 2014)Since golden eagles frequently prey upon weak mor-ibund or dead animals they undergo an increasedexposure to lead shot or bullet fragments enclosed inthe flesh of hunter-crippled game and prey carcassesIt is also general practice to eviscerate hunted wildlifein the field thereby leaving behind lead-contaminatedoffal (digestive tract heart lungs) that may be readilyingested by terrestrial raptors if not buried properlyDuring the hunting season about 10 000 shot reddeer roe deer chamois and ibex provide about 100tons of offal of which part may not be properly buriedand therefore available to the 120 breeding pairs ofgolden eagles in the Grisons The oral uptake of leadshot and bullet fragments from these sources maycause severe poisonings (Garcia-Fernandez et al 1997Pattee et al 2006 Stansley and Murphy 2011) Otherpossible routes of lead uptake seem much less likelyNonlethal lead shot at golden eagles and incorporatedinto the body has been found only in one case Leademissions during military exercises is not available tothe birds together with their food and are expected tocontribute minimally to the lead burden of goldeneagles

We conclude that in the Alps most golden eaglestake up lead from spent ammunition in carcasses ortheir offal in sublethal quantities throughout their life(see the high bone levels of almost all eagles examinedin this study) and a few in lethal quantities leading toacute lead poisoning (see table 1 and Bezzel and Fuumlnf-stuumlck 1995 Zechner et al 2005 Kenntner et al 2007)

Besides causing directmortality through the inges-tion of high amounts of lead the intake of sublethalamounts may affect avian populations by altering cog-nition and behaviour diminishing reproductive suc-cess and causing diseases as well as starvation ortraumatic events or by subjecting the exposed birds toundue predation (Gangoso et al 2009 Rodriguez-Ramos Fernandez et al 2011) The successive accumu-lation of larger sublethal quantities early in life mayindeed have resulted in a higher mortality (seefigure 2) However very little is known about theeffects of sublethal lead burdens in any wild bird

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Environ Res Lett 10 (2015) 034003 MMMadry et al

population (Haig et al 2014) Although the goldeneagle population in the study area has increased in thelast 60 years (eg +10 since the census in 1990ndash1992Haller (1996)) and prosper at high density the intro-duction of lead-free ammunition for upland huntingin the investigated Alpine regionswould greatly reducethe overall lead burden and contribute to the health ofscavenging raptors in general This would be particu-larly important for bearded vultures which are beingre-introduced from captive breeding programs andstill represent a very small and vulnerable althoughincreasing population in the Alps (Schaub et al 2009)Their very high bone lead concentrations (see above)need further attention

Acknowledgments

We thank David Kistler (Swiss Federal Institute ofAquatic Science and Technology) for access to theMicrowave Digestion System Fabian von Kaenel forhis help with the ICP-MSmeasurements and RichardHoop (Institute of Veterinary Bacteriology Universityof Zurich) for the sampling of birds We thank theauthorities of the Cantonal Fish and Game Depart-ments and the many gamekeepers who helped collect-ing dead and moribund golden eagles and bonesamples of ibexes Werner Degonda performed theautopsies in Chur Veterinarians of the Universities ofBerne and Zurich provided additional data particu-larly Janne Schoumlning RomanMeier Ulrike Cyrus andJessica Gull Enrico Bassi from the Stelvio NationalPark and Daniel Hegglin Stiftung Pro Bartgeierprovided data from bones of bearded vultures Injuredor moribund birds were maintained in bird carestations by Christoph Meier Erich Widmer VreniMattmann and Andi Lischke Lorenzo VinciguerraUeli Schneppat and Reneacute Heim of the Natural HistoryMuseums of St Gallen Grisons and Lucerne preparedbone samples of some golden eagles and beardedvultures Marco Lanfranchi of the Department forNature and Environment of the Canton of Grisonsand Reto Giulio Meuli of the Swiss National SoilMonitoring Network (NABO) provided soil samplesHans Schmid Swiss Ornithological Institute helpedto coordinate the project Fraumlnzi Korner-NievergeltSwiss Ornithological Institute helped with data analy-sis and statistics

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Bassi E and FerloniM2012 Lrsquoesposizione dei rapaci al piombo ilcaso della provincia di Sondrio Il PiomboNelleMunizioni daCaccia Problematiche e Possibili Soluzioni Rapporti ISPRA edAAndreotti and FBorghesi 53ndash4

Bassi E FerloniM andBianchi A 2013 Lrsquointossicazione da piombonei grandi rapaci necrofagi Info Gipeto 30 31

Bassi E FerloniMGugiatti A Pedrotti L Di GiancamilloMandGrilli G Il rischio di Saturnismo negli uccelli necrofagi inrelazione alle attualimodalitagrave di caccia degli ungulati AttiXVIConvegno Italiano diOrnitologia edRTinarelli

AAndreotti NBaccetti LMelega F Roscelli L Serra andMZenatelloAtti XVI Convegno Italiano diOrnitologia (inpress)

Bezzel E and FuumlnfstuumlckH J 1995Alpine SteinadlerAquila chrysaetosdurch Bleivergiftung gefaumlhrdet J Ornithol 136 294ndash6

Carpenter JW PatteeOH Fritts SH Rattner BAWiemeyer SNRoyle J A and SmithMR2003 Experimental lead poisoningin turkey vultures (Cathartes aura) JWildl Dis 39 96ndash104

Cerradelo SMunoz E To-Figueras JMateoR andGuitart R 1992Intoxicacion por ingestion de perdigones de plomo en dosaguilas realesDontildeana Acta Vertebrata 19 122ndash7

ChurchMEGwiazda R RisebroughRW SorensonKChamberlainCP Farry SHeinrichWRideout BA andSmithDR2006Ammunition is the principal source of leadaccumulated byCalifornia condors re-introduced to thewildEnviron Sci Technol 40 6143ndash50

ClarkA J and Scheuhammer AM2003 Lead poisoning in upland-foraging birds of prey in CanadaEcotoxicology 12 23ndash30

Craig THConnelly JWCraig EH and Parker T L 1990 Leadconcentrations in golden and bald eaglesWilson Bull 102130ndash3

Ethier A L Braune BM Scheuhammer AMandBondDE2007Comparison of lead residues among avian bonesEnvironPollut 145 915ndash9

FinkelsteinME et al 2010 Feather lead concentrations and207Pb206Pb ratios reveal lead exposure history of Californiacondors (Gymnogyps californianus)Environ Sci Technol 442639ndash47

Fisher I J PainD J andThomasVG2006A review of lead poisoningfrom ammunition sources in terrestrial birdsBiol Cons 131421ndash32

Franson J C Sileo L PatteeOHandMoore J F 1983 Effects ofchronic dietary lead in American kestrels (Falco sparverius)JWildl Dis 19 110ndash3

Gangoso L Alvarez-Lloret P Rodriacuteguez-Navarro AAMateoRHiraldo F andDonaacutezar J A 2009 Long-term effects of leadpoisoning on bonemineralization in vultures exposed toammunition sources Environ Pollut 157 569ndash74

Garcia-Fernandez A JMotas-GuzmanMNavas IMaria-Mojica PLunaA and Sanchez-Garcia J A 1997 Environmental expo-sure and distribution of lead in four species of raptors inSoutheastern SpainArch Environ Contam Toxicol 3376ndash82

GelmanACarlin J B SternH SDunsonDB Vehtari A andRubinDB 2014BayesianData Analysis 3rd edn (NewYorkCRCPress)

GelmanA andHill J 2007Data Analysis Using Regression andMultilevelHierarchicalModels (Cambridge CambridgeUni-verstiy Press)

Haig SMDrsquoElia J Eagles-SmithC Fait JMGervais J HerringGRivers JWand Schulz JH 2014The persistent problemof leadpoisoning in birds from ammunition and fishing tackleCondor 116 408ndash28

HallerH 1996Der Steinadler inGraubuumlnden Langfristige Untersu-chungen zur Populationsoumlkologie vonAquila chrysaetos imZentrumderAlpenOrnithol Beob Beiheft 9 1ndash168

Harmata AR andRestaniM2013 Leadmercury selenium andother trace elements in tisssue of golden eagles from South-westernMontana USA JWildl Dis 49 114ndash24

HuntG BurnhamW ParishCN BurnhamKKMutch B andOaks J L 2006 Bullet fragments in deer remains implicationsfor lead exposure in scavengersWildl Soc Bull 34 167ndash70

Kendall R J Lacher TE BunckCDaniel B Driver CGrueCELeighton F and StansleyW1996An ecological risk assessmentof lead shot exposure in non-waterfowl avian species uplandgame birds and raptorsEnviron Toxicol Chem 151 1ndash20

KenntnerN Crettenand Y FuumlnfstuumlckH J JanovskyMandTataruch F 2007 Lead poisoning and heavymetal exposure ofgolden eagles (Aquila chrysaetos) from the EuropeanAlpsJ Ornithol 148 173ndash7

Kramer J L andRedig PT 1997 Sixteen years of lead poisoning ineagles 1980ndash1995 an epizootiologic view J Raptor Res 31327ndash32

8

Environ Res Lett 10 (2015) 034003 MMMadry et al

Figure 1 Frequency distribution of lead concentrations in the liver (A) kidney (B) and bones (C) of golden eagles and eagle owlsNote the logarithmic y-axis Dotted lines indicate literature thresholds of elevated levels (6 μg gminus1 for liver and kidney 675 μg gminus1 forbones) see table 1 and text Lead concentration in liver kidney and bones all differ significantly between the two species (non-parametricMannndashWhitneyU-test plt0001) In addition the high value for liver and kidney from table 1 is also shown

4

Environ Res Lett 10 (2015) 034003 MMMadry et al

golden eagles ranged from 02 to 841 μg gminus1 with amedian value of 114 μg gminus1 (N= 25) The respectiveconcentrations in eagle owls ranged from 005 to041 μg gminus1 with amedian of only 014 μg gminus1 (N= 15)The lead content in the kidney of golden eagles rangedfrom 018 to 332 μg gminus1 with a median value of099 μg gminus1 (N= 24) The respective concentrations ineagle owls ranged from 010 to 099 μg gminus1 with amed-ian of only 023 μg gminus1 (N= 15) The largest differencebetween the two predatory bird species was detectedupon analysis of their bones In golden eagles the leadcontent in this mineralized tissue ranged from 122 to3840 μg gminus1 (median concentration 1245 μg gminus1N= 17) whereas in eagle owls the lead content of thebones ranged from 046 to 229 μg gminus1 (median con-centration 128 μg gminus1 N= 13) Only the lowestgolden eagle value was within the range of eagle owlvalues

Lead incorporated in the bones is thought to inte-grate all episodes of exposure within the life of an indi-vidual Therefore due to the continued accumulationof this heavymetal inmineralized tissues the lead con-tent of bones is expected to steadily increase with age(Rodriguez-Ramos Fernandez et al 2011) Howeveramong the golden eagles we observed an inverse trendof lead concentrations in the bones as the animals pro-gress from juvenile and sub-adult periods of life (lt5years old) to the adult stage (⩾5 years old figure 2) Inparticular the younger birds could be clearly sepa-rated in a group with low lead concentrations in thebones and another group with increased lead burden(gt25 μg gminus1) This pattern of lead accumulation may

indicate that young golden eagles with lead contents inbone exceeding 25 μg gminus1 may suffer from increasedmortality This view is confirmed by the observationthat the expected age-dependent increase of lead con-centrations in the bones is re-established when thebirds with values gt25 μg gminus1 are omitted from the cal-culations (figure 2)

The concentration of lead in bones of prey animalsfound in golden eagle and eagle owl nests (mean plusmn SD256 μg gminus1 plusmn 135 for golden eagle prey and295 μg gminus1 plusmn 063 for eagle owl prey) was indis-tinguishable from that of eagle owl bones but sig-nificantly lower than the values of golden eagle bones(figure 3) Lead concentration in bones of Alpineibexes was significantly lower than in prey animals oreagle owls (figure 3) There was no significant correla-tion between lead concentration in bones and the ageof Alpine ibexes (p= 086 linear regression)

The isotope ratios of 207Pb208Pb and 206Pb208Pbfound in the bones of golden eagles were statisticallyindistinguishable from those determined for ammuni-tion (figure 4) The isotope ratios in bones of prey ani-mals of the golden eagle ibexes eagle owls and in soilsamples were significantly different from the lead iso-tope ratios of both golden eagles and ammunition(figure 4) Prey animals of eagle owls were inter-mediate and statistically indistinguishable in their Pbisotope ratios from ammunition golden eagles andeagle owl bones In detail the isotope ratios in bones ofAlpine ibexes and of golden eagle prey animals aresimilar among each other Eagle owl bones showed alarge variation in both Pb isotope ratios and were sta-tistically different from bones of golden eagle preyibexes and golden eagles and from ammunition Soilsamples showed a very small variation in Pb isotoperatios and differed significantly from ammunitionand bones of golden eagles golden eagle prey eagleowl prey (figure 4)

There was no correlation between the lead isotoperatios and the lead concentration in bones of goldeneagles (p= 027 for 207Pb208Pb and p= 034 for206Pb208Pb linear regression) or in bones of eagleowls their prey Alpine ibex (taken together or sepa-rately) or soil samples (pgt 012 in all analyses linearregression) In particular the three soil samples fromsediments of a lake contaminated by the abandonedore mine showed very high lead concentrations(118ndash503 μg gminus1) but their isotope ratios did not dif-fer from the other soil samples (supplementary datatable S3)

4Discussion

In this study we found three cases of golden eagles inthe Alps with acute signs of lead poisoning confirmedby excessive concentrations of lead in blood liver andkidney (table 1) Once absorbed in the small intestinelead binds to red blood cells before being redistributed

Figure 2Bone lead concentrations of immature and subadult(lt5 years old) versus adult (⩾5 years old) golden eagles If thevalues gt25 μg gminus1 are omitted adult birds have significantlyhigher bone lead concentrations (958ndash3223 μg gminus1median1264 μg gminus1N= 9) than the immature and subadult animals(122ndash704 μg gminus1median 468 μg gminus1N= 4 non-para-metricMannndashWhitneyU-test p= 0007)

5

Environ Res Lett 10 (2015) 034003 MMMadry et al

to highly perfused organs First there is a rapidexchange between the circulating blood and theparenchyma of liver kidney and the brain (Namet al 2012) By replacement of calcium ions this heavymetal is then slowly transferred into the bones whichultimately contain gt90 of the overall body burdenWhereas lead in liver and kidney has a turnover rate ofweeks to months bones constitute a long-term depot(Ethier et al 2007 Rodriguez-Ramos Fernandezet al 2011) As a consequence lead levels in blood aremeasured for the diagnosis of poisoning in living birdswhereas analyses of liver and kidney are used for thepost-mortem confirmation (see table 1)

The concentrations of lead in the bones of raptorsare usually not directly related to current episodes ofexposure (Ethier et al 2007 Gangoso et al 2009) butcan increase rapidly after lead ingestion (Sandersonand Bellrose 1986) Concentrations gt10 μg gminus1 in

bone tissue are considered to be elevated and con-centrations gt20 μg gminus1 are often observed after lethalpoisoning (Mateo et al 2003 Rodriguez-Ramos Fer-nandez et al 2011) Interestingly the lead concentra-tions in the bones of golden eagles found in our study(median of 1245 μg gminus1 dry weight) were substantiallyhigher than those previously reported in the literaturefor the same species For example Mateo et al (2003)detected bone concentrations between 049 and497 μg gminus1 dry weight in golden eagles found in SpainWayland et al (1999) divided the birds into those withbackground hepatic lead levels (lt6 μg gminus1) and thosewith elevated hepatic levels (gt6 μg gminus1) Mean bonelead concentrations in this Canadian study were41 μg gminus1 for the former group and 97 μg gminus1 for thelatter Clark and Scheuhammer (2003) found inCanada that 5 out of 9 birds had bone lead concentra-tions gt675 μg gminus1 whereas we found in our study a

Figure 3Mean bone lead concentration of golden eagles and eagle owls comparedwith their prey Lines are 95 confidence intervals(if not shown they are smaller than the symbol)Means not sharing the same symbol are significantly different from each other at theplt 0001 level Numbers in parentheses are sample sizes

Figure 4Mean ratio of 207Pb208Pb and 206Pb208Pb found in bones of golden eagles eagle owls their prey and inAlpine ibex as wellas in ammunition and soil Ellipses are 95 confidence intervals A sample is significantly different from another sample if themean isnot includedwithin the 95 confidence ellipse of the other sample

6

Environ Res Lett 10 (2015) 034003 MMMadry et al

higher proportion (14 out of 17 specimens) with con-centrations in the bone gt675 μg gminus1

Other scavenging raptors are also likely to take uplead (see Rodriguez-Ramos Fernandez et al 2011)Among four examined bearded vultures from theAlps only one had a low lead concentration in bones(650 μg gminus1) while three had very high values(3890ndash10004 μg gminus1 Bassi et al (2013) Bassi et al inpress own unpublished data) Hence the bone leadconcentrations found in systematically collected deadgolden eagles in the eastern Swiss Alps was exception-ally high compared to those found in other goldeneagle populations In liver and kidney lead concentra-tions of golden eagles without signs of lead intoxica-tion did not exceed literature thresholds of elevatedlevels but were significantly higher than in eagle owlsHence although no signs of acute poisoning wereapparent even kidney and liver levels were elevatedcompared to another predator bird

Lead concentrations in bones of golden eagle preyanimals were gt10-fold lower than in golden eaglebones and ibex bones contained even gt20-fold lesslead (the median of 047 μg gminus1 found in this studycompares well with themedian of 059 μg gminus1 found byTataruch and Onderscheka (1995) in the same area)In contrast bones of eagle owl prey contained evenslightly more lead than eagle owl bones Therefore thelarge difference in bone lead concentration betweenthe two predators cannot be explained by differencesin lead concentration of their prey Part of the differ-ence between golden eagles and eagle owls in bone leadconcentration may be due to the fact that gastricpH values of owls are not quite as low as in raptors(Fisher et al 2006 Rodriguez-Ramos Fernandezet al 2011) and that owls regurgitate bones while rap-tors partly digest and partly regurgitate bones Hencethe absorption of ingested lead may be more completein raptors than in owls

The examination of lead isotope ratios revealedthat lead of golden eagles was most similar to that ofammunition used in the study area and differed fromthe isotope signature of golden eagle prey and soilsamples (even those with high lead concentrationsfrom ore mines or natural occurrence) Surprisinglythere was no change in isotope signature with increas-ing lead concentration in bones of golden eagles (orany other sample) This indicates that the source oflead ie from ammunition remains the same irre-spective of the amount of lead up-take

Taken together our findings indicate that lead ingolden eagles originates from ammunition and is notthe consequence of a bioaccumulation of genericallyavailable lead in the environment (eg from old oremine or aerial deposition of industrial lead) The find-ing that lead is accumulated in very high amounts inbones of golden eagles and is present in higheramounts than in another predator species even inliver and kidney suggests a frequent uptake of sub-lethal amounts of lead The lead concentration in

segments of wing feathers showed an irregular patternindicating an episodic rather than continuous leaduptake (ownunpublished data)

There are two main sources of ammunition leadfor golden eagles in the Alps which cannot be dis-tinguished by this study First golden eagles could feedon animals shot with lead pellets which were notretrieved or whose carcasses were left in the environ-ment (eg fox carcasses after skinning) Secondgolden eagles could take up lead fragments from ani-mals or their offal shot with lead bullets still themainammunition of hunters in the study area

When striking their targets conventional lead-based rifle bullets partly disintegrate intometallic frag-ments causing a widespread contamination of animaltissues (Church et al 2006 Hunt et al 2006 Bassi andFerloni 2012 Trinogga et al 2013 Haig et al 2014)Since golden eagles frequently prey upon weak mor-ibund or dead animals they undergo an increasedexposure to lead shot or bullet fragments enclosed inthe flesh of hunter-crippled game and prey carcassesIt is also general practice to eviscerate hunted wildlifein the field thereby leaving behind lead-contaminatedoffal (digestive tract heart lungs) that may be readilyingested by terrestrial raptors if not buried properlyDuring the hunting season about 10 000 shot reddeer roe deer chamois and ibex provide about 100tons of offal of which part may not be properly buriedand therefore available to the 120 breeding pairs ofgolden eagles in the Grisons The oral uptake of leadshot and bullet fragments from these sources maycause severe poisonings (Garcia-Fernandez et al 1997Pattee et al 2006 Stansley and Murphy 2011) Otherpossible routes of lead uptake seem much less likelyNonlethal lead shot at golden eagles and incorporatedinto the body has been found only in one case Leademissions during military exercises is not available tothe birds together with their food and are expected tocontribute minimally to the lead burden of goldeneagles

We conclude that in the Alps most golden eaglestake up lead from spent ammunition in carcasses ortheir offal in sublethal quantities throughout their life(see the high bone levels of almost all eagles examinedin this study) and a few in lethal quantities leading toacute lead poisoning (see table 1 and Bezzel and Fuumlnf-stuumlck 1995 Zechner et al 2005 Kenntner et al 2007)

Besides causing directmortality through the inges-tion of high amounts of lead the intake of sublethalamounts may affect avian populations by altering cog-nition and behaviour diminishing reproductive suc-cess and causing diseases as well as starvation ortraumatic events or by subjecting the exposed birds toundue predation (Gangoso et al 2009 Rodriguez-Ramos Fernandez et al 2011) The successive accumu-lation of larger sublethal quantities early in life mayindeed have resulted in a higher mortality (seefigure 2) However very little is known about theeffects of sublethal lead burdens in any wild bird

7

Environ Res Lett 10 (2015) 034003 MMMadry et al

population (Haig et al 2014) Although the goldeneagle population in the study area has increased in thelast 60 years (eg +10 since the census in 1990ndash1992Haller (1996)) and prosper at high density the intro-duction of lead-free ammunition for upland huntingin the investigated Alpine regionswould greatly reducethe overall lead burden and contribute to the health ofscavenging raptors in general This would be particu-larly important for bearded vultures which are beingre-introduced from captive breeding programs andstill represent a very small and vulnerable althoughincreasing population in the Alps (Schaub et al 2009)Their very high bone lead concentrations (see above)need further attention

Acknowledgments

We thank David Kistler (Swiss Federal Institute ofAquatic Science and Technology) for access to theMicrowave Digestion System Fabian von Kaenel forhis help with the ICP-MSmeasurements and RichardHoop (Institute of Veterinary Bacteriology Universityof Zurich) for the sampling of birds We thank theauthorities of the Cantonal Fish and Game Depart-ments and the many gamekeepers who helped collect-ing dead and moribund golden eagles and bonesamples of ibexes Werner Degonda performed theautopsies in Chur Veterinarians of the Universities ofBerne and Zurich provided additional data particu-larly Janne Schoumlning RomanMeier Ulrike Cyrus andJessica Gull Enrico Bassi from the Stelvio NationalPark and Daniel Hegglin Stiftung Pro Bartgeierprovided data from bones of bearded vultures Injuredor moribund birds were maintained in bird carestations by Christoph Meier Erich Widmer VreniMattmann and Andi Lischke Lorenzo VinciguerraUeli Schneppat and Reneacute Heim of the Natural HistoryMuseums of St Gallen Grisons and Lucerne preparedbone samples of some golden eagles and beardedvultures Marco Lanfranchi of the Department forNature and Environment of the Canton of Grisonsand Reto Giulio Meuli of the Swiss National SoilMonitoring Network (NABO) provided soil samplesHans Schmid Swiss Ornithological Institute helpedto coordinate the project Fraumlnzi Korner-NievergeltSwiss Ornithological Institute helped with data analy-sis and statistics

References

Bassi E and FerloniM2012 Lrsquoesposizione dei rapaci al piombo ilcaso della provincia di Sondrio Il PiomboNelleMunizioni daCaccia Problematiche e Possibili Soluzioni Rapporti ISPRA edAAndreotti and FBorghesi 53ndash4

Bassi E FerloniM andBianchi A 2013 Lrsquointossicazione da piombonei grandi rapaci necrofagi Info Gipeto 30 31

Bassi E FerloniMGugiatti A Pedrotti L Di GiancamilloMandGrilli G Il rischio di Saturnismo negli uccelli necrofagi inrelazione alle attualimodalitagrave di caccia degli ungulati AttiXVIConvegno Italiano diOrnitologia edRTinarelli

AAndreotti NBaccetti LMelega F Roscelli L Serra andMZenatelloAtti XVI Convegno Italiano diOrnitologia (inpress)

Bezzel E and FuumlnfstuumlckH J 1995Alpine SteinadlerAquila chrysaetosdurch Bleivergiftung gefaumlhrdet J Ornithol 136 294ndash6

Carpenter JW PatteeOH Fritts SH Rattner BAWiemeyer SNRoyle J A and SmithMR2003 Experimental lead poisoningin turkey vultures (Cathartes aura) JWildl Dis 39 96ndash104

Cerradelo SMunoz E To-Figueras JMateoR andGuitart R 1992Intoxicacion por ingestion de perdigones de plomo en dosaguilas realesDontildeana Acta Vertebrata 19 122ndash7

ChurchMEGwiazda R RisebroughRW SorensonKChamberlainCP Farry SHeinrichWRideout BA andSmithDR2006Ammunition is the principal source of leadaccumulated byCalifornia condors re-introduced to thewildEnviron Sci Technol 40 6143ndash50

ClarkA J and Scheuhammer AM2003 Lead poisoning in upland-foraging birds of prey in CanadaEcotoxicology 12 23ndash30

Craig THConnelly JWCraig EH and Parker T L 1990 Leadconcentrations in golden and bald eaglesWilson Bull 102130ndash3

Ethier A L Braune BM Scheuhammer AMandBondDE2007Comparison of lead residues among avian bonesEnvironPollut 145 915ndash9

FinkelsteinME et al 2010 Feather lead concentrations and207Pb206Pb ratios reveal lead exposure history of Californiacondors (Gymnogyps californianus)Environ Sci Technol 442639ndash47

Fisher I J PainD J andThomasVG2006A review of lead poisoningfrom ammunition sources in terrestrial birdsBiol Cons 131421ndash32

Franson J C Sileo L PatteeOHandMoore J F 1983 Effects ofchronic dietary lead in American kestrels (Falco sparverius)JWildl Dis 19 110ndash3

Gangoso L Alvarez-Lloret P Rodriacuteguez-Navarro AAMateoRHiraldo F andDonaacutezar J A 2009 Long-term effects of leadpoisoning on bonemineralization in vultures exposed toammunition sources Environ Pollut 157 569ndash74

Garcia-Fernandez A JMotas-GuzmanMNavas IMaria-Mojica PLunaA and Sanchez-Garcia J A 1997 Environmental expo-sure and distribution of lead in four species of raptors inSoutheastern SpainArch Environ Contam Toxicol 3376ndash82

GelmanACarlin J B SternH SDunsonDB Vehtari A andRubinDB 2014BayesianData Analysis 3rd edn (NewYorkCRCPress)

GelmanA andHill J 2007Data Analysis Using Regression andMultilevelHierarchicalModels (Cambridge CambridgeUni-verstiy Press)

Haig SMDrsquoElia J Eagles-SmithC Fait JMGervais J HerringGRivers JWand Schulz JH 2014The persistent problemof leadpoisoning in birds from ammunition and fishing tackleCondor 116 408ndash28

HallerH 1996Der Steinadler inGraubuumlnden Langfristige Untersu-chungen zur Populationsoumlkologie vonAquila chrysaetos imZentrumderAlpenOrnithol Beob Beiheft 9 1ndash168

Harmata AR andRestaniM2013 Leadmercury selenium andother trace elements in tisssue of golden eagles from South-westernMontana USA JWildl Dis 49 114ndash24

HuntG BurnhamW ParishCN BurnhamKKMutch B andOaks J L 2006 Bullet fragments in deer remains implicationsfor lead exposure in scavengersWildl Soc Bull 34 167ndash70

Kendall R J Lacher TE BunckCDaniel B Driver CGrueCELeighton F and StansleyW1996An ecological risk assessmentof lead shot exposure in non-waterfowl avian species uplandgame birds and raptorsEnviron Toxicol Chem 151 1ndash20

KenntnerN Crettenand Y FuumlnfstuumlckH J JanovskyMandTataruch F 2007 Lead poisoning and heavymetal exposure ofgolden eagles (Aquila chrysaetos) from the EuropeanAlpsJ Ornithol 148 173ndash7

Kramer J L andRedig PT 1997 Sixteen years of lead poisoning ineagles 1980ndash1995 an epizootiologic view J Raptor Res 31327ndash32

8

Environ Res Lett 10 (2015) 034003 MMMadry et al

golden eagles ranged from 02 to 841 μg gminus1 with amedian value of 114 μg gminus1 (N= 25) The respectiveconcentrations in eagle owls ranged from 005 to041 μg gminus1 with amedian of only 014 μg gminus1 (N= 15)The lead content in the kidney of golden eagles rangedfrom 018 to 332 μg gminus1 with a median value of099 μg gminus1 (N= 24) The respective concentrations ineagle owls ranged from 010 to 099 μg gminus1 with amed-ian of only 023 μg gminus1 (N= 15) The largest differencebetween the two predatory bird species was detectedupon analysis of their bones In golden eagles the leadcontent in this mineralized tissue ranged from 122 to3840 μg gminus1 (median concentration 1245 μg gminus1N= 17) whereas in eagle owls the lead content of thebones ranged from 046 to 229 μg gminus1 (median con-centration 128 μg gminus1 N= 13) Only the lowestgolden eagle value was within the range of eagle owlvalues

Lead incorporated in the bones is thought to inte-grate all episodes of exposure within the life of an indi-vidual Therefore due to the continued accumulationof this heavymetal inmineralized tissues the lead con-tent of bones is expected to steadily increase with age(Rodriguez-Ramos Fernandez et al 2011) Howeveramong the golden eagles we observed an inverse trendof lead concentrations in the bones as the animals pro-gress from juvenile and sub-adult periods of life (lt5years old) to the adult stage (⩾5 years old figure 2) Inparticular the younger birds could be clearly sepa-rated in a group with low lead concentrations in thebones and another group with increased lead burden(gt25 μg gminus1) This pattern of lead accumulation may

indicate that young golden eagles with lead contents inbone exceeding 25 μg gminus1 may suffer from increasedmortality This view is confirmed by the observationthat the expected age-dependent increase of lead con-centrations in the bones is re-established when thebirds with values gt25 μg gminus1 are omitted from the cal-culations (figure 2)

The concentration of lead in bones of prey animalsfound in golden eagle and eagle owl nests (mean plusmn SD256 μg gminus1 plusmn 135 for golden eagle prey and295 μg gminus1 plusmn 063 for eagle owl prey) was indis-tinguishable from that of eagle owl bones but sig-nificantly lower than the values of golden eagle bones(figure 3) Lead concentration in bones of Alpineibexes was significantly lower than in prey animals oreagle owls (figure 3) There was no significant correla-tion between lead concentration in bones and the ageof Alpine ibexes (p= 086 linear regression)

The isotope ratios of 207Pb208Pb and 206Pb208Pbfound in the bones of golden eagles were statisticallyindistinguishable from those determined for ammuni-tion (figure 4) The isotope ratios in bones of prey ani-mals of the golden eagle ibexes eagle owls and in soilsamples were significantly different from the lead iso-tope ratios of both golden eagles and ammunition(figure 4) Prey animals of eagle owls were inter-mediate and statistically indistinguishable in their Pbisotope ratios from ammunition golden eagles andeagle owl bones In detail the isotope ratios in bones ofAlpine ibexes and of golden eagle prey animals aresimilar among each other Eagle owl bones showed alarge variation in both Pb isotope ratios and were sta-tistically different from bones of golden eagle preyibexes and golden eagles and from ammunition Soilsamples showed a very small variation in Pb isotoperatios and differed significantly from ammunitionand bones of golden eagles golden eagle prey eagleowl prey (figure 4)

There was no correlation between the lead isotoperatios and the lead concentration in bones of goldeneagles (p= 027 for 207Pb208Pb and p= 034 for206Pb208Pb linear regression) or in bones of eagleowls their prey Alpine ibex (taken together or sepa-rately) or soil samples (pgt 012 in all analyses linearregression) In particular the three soil samples fromsediments of a lake contaminated by the abandonedore mine showed very high lead concentrations(118ndash503 μg gminus1) but their isotope ratios did not dif-fer from the other soil samples (supplementary datatable S3)

4Discussion

In this study we found three cases of golden eagles inthe Alps with acute signs of lead poisoning confirmedby excessive concentrations of lead in blood liver andkidney (table 1) Once absorbed in the small intestinelead binds to red blood cells before being redistributed

Figure 2Bone lead concentrations of immature and subadult(lt5 years old) versus adult (⩾5 years old) golden eagles If thevalues gt25 μg gminus1 are omitted adult birds have significantlyhigher bone lead concentrations (958ndash3223 μg gminus1median1264 μg gminus1N= 9) than the immature and subadult animals(122ndash704 μg gminus1median 468 μg gminus1N= 4 non-para-metricMannndashWhitneyU-test p= 0007)

5

Environ Res Lett 10 (2015) 034003 MMMadry et al

to highly perfused organs First there is a rapidexchange between the circulating blood and theparenchyma of liver kidney and the brain (Namet al 2012) By replacement of calcium ions this heavymetal is then slowly transferred into the bones whichultimately contain gt90 of the overall body burdenWhereas lead in liver and kidney has a turnover rate ofweeks to months bones constitute a long-term depot(Ethier et al 2007 Rodriguez-Ramos Fernandezet al 2011) As a consequence lead levels in blood aremeasured for the diagnosis of poisoning in living birdswhereas analyses of liver and kidney are used for thepost-mortem confirmation (see table 1)

The concentrations of lead in the bones of raptorsare usually not directly related to current episodes ofexposure (Ethier et al 2007 Gangoso et al 2009) butcan increase rapidly after lead ingestion (Sandersonand Bellrose 1986) Concentrations gt10 μg gminus1 in

bone tissue are considered to be elevated and con-centrations gt20 μg gminus1 are often observed after lethalpoisoning (Mateo et al 2003 Rodriguez-Ramos Fer-nandez et al 2011) Interestingly the lead concentra-tions in the bones of golden eagles found in our study(median of 1245 μg gminus1 dry weight) were substantiallyhigher than those previously reported in the literaturefor the same species For example Mateo et al (2003)detected bone concentrations between 049 and497 μg gminus1 dry weight in golden eagles found in SpainWayland et al (1999) divided the birds into those withbackground hepatic lead levels (lt6 μg gminus1) and thosewith elevated hepatic levels (gt6 μg gminus1) Mean bonelead concentrations in this Canadian study were41 μg gminus1 for the former group and 97 μg gminus1 for thelatter Clark and Scheuhammer (2003) found inCanada that 5 out of 9 birds had bone lead concentra-tions gt675 μg gminus1 whereas we found in our study a

Figure 3Mean bone lead concentration of golden eagles and eagle owls comparedwith their prey Lines are 95 confidence intervals(if not shown they are smaller than the symbol)Means not sharing the same symbol are significantly different from each other at theplt 0001 level Numbers in parentheses are sample sizes

Figure 4Mean ratio of 207Pb208Pb and 206Pb208Pb found in bones of golden eagles eagle owls their prey and inAlpine ibex as wellas in ammunition and soil Ellipses are 95 confidence intervals A sample is significantly different from another sample if themean isnot includedwithin the 95 confidence ellipse of the other sample

6

Environ Res Lett 10 (2015) 034003 MMMadry et al

higher proportion (14 out of 17 specimens) with con-centrations in the bone gt675 μg gminus1

Other scavenging raptors are also likely to take uplead (see Rodriguez-Ramos Fernandez et al 2011)Among four examined bearded vultures from theAlps only one had a low lead concentration in bones(650 μg gminus1) while three had very high values(3890ndash10004 μg gminus1 Bassi et al (2013) Bassi et al inpress own unpublished data) Hence the bone leadconcentrations found in systematically collected deadgolden eagles in the eastern Swiss Alps was exception-ally high compared to those found in other goldeneagle populations In liver and kidney lead concentra-tions of golden eagles without signs of lead intoxica-tion did not exceed literature thresholds of elevatedlevels but were significantly higher than in eagle owlsHence although no signs of acute poisoning wereapparent even kidney and liver levels were elevatedcompared to another predator bird

Lead concentrations in bones of golden eagle preyanimals were gt10-fold lower than in golden eaglebones and ibex bones contained even gt20-fold lesslead (the median of 047 μg gminus1 found in this studycompares well with themedian of 059 μg gminus1 found byTataruch and Onderscheka (1995) in the same area)In contrast bones of eagle owl prey contained evenslightly more lead than eagle owl bones Therefore thelarge difference in bone lead concentration betweenthe two predators cannot be explained by differencesin lead concentration of their prey Part of the differ-ence between golden eagles and eagle owls in bone leadconcentration may be due to the fact that gastricpH values of owls are not quite as low as in raptors(Fisher et al 2006 Rodriguez-Ramos Fernandezet al 2011) and that owls regurgitate bones while rap-tors partly digest and partly regurgitate bones Hencethe absorption of ingested lead may be more completein raptors than in owls

The examination of lead isotope ratios revealedthat lead of golden eagles was most similar to that ofammunition used in the study area and differed fromthe isotope signature of golden eagle prey and soilsamples (even those with high lead concentrationsfrom ore mines or natural occurrence) Surprisinglythere was no change in isotope signature with increas-ing lead concentration in bones of golden eagles (orany other sample) This indicates that the source oflead ie from ammunition remains the same irre-spective of the amount of lead up-take

Taken together our findings indicate that lead ingolden eagles originates from ammunition and is notthe consequence of a bioaccumulation of genericallyavailable lead in the environment (eg from old oremine or aerial deposition of industrial lead) The find-ing that lead is accumulated in very high amounts inbones of golden eagles and is present in higheramounts than in another predator species even inliver and kidney suggests a frequent uptake of sub-lethal amounts of lead The lead concentration in

segments of wing feathers showed an irregular patternindicating an episodic rather than continuous leaduptake (ownunpublished data)

There are two main sources of ammunition leadfor golden eagles in the Alps which cannot be dis-tinguished by this study First golden eagles could feedon animals shot with lead pellets which were notretrieved or whose carcasses were left in the environ-ment (eg fox carcasses after skinning) Secondgolden eagles could take up lead fragments from ani-mals or their offal shot with lead bullets still themainammunition of hunters in the study area

When striking their targets conventional lead-based rifle bullets partly disintegrate intometallic frag-ments causing a widespread contamination of animaltissues (Church et al 2006 Hunt et al 2006 Bassi andFerloni 2012 Trinogga et al 2013 Haig et al 2014)Since golden eagles frequently prey upon weak mor-ibund or dead animals they undergo an increasedexposure to lead shot or bullet fragments enclosed inthe flesh of hunter-crippled game and prey carcassesIt is also general practice to eviscerate hunted wildlifein the field thereby leaving behind lead-contaminatedoffal (digestive tract heart lungs) that may be readilyingested by terrestrial raptors if not buried properlyDuring the hunting season about 10 000 shot reddeer roe deer chamois and ibex provide about 100tons of offal of which part may not be properly buriedand therefore available to the 120 breeding pairs ofgolden eagles in the Grisons The oral uptake of leadshot and bullet fragments from these sources maycause severe poisonings (Garcia-Fernandez et al 1997Pattee et al 2006 Stansley and Murphy 2011) Otherpossible routes of lead uptake seem much less likelyNonlethal lead shot at golden eagles and incorporatedinto the body has been found only in one case Leademissions during military exercises is not available tothe birds together with their food and are expected tocontribute minimally to the lead burden of goldeneagles

We conclude that in the Alps most golden eaglestake up lead from spent ammunition in carcasses ortheir offal in sublethal quantities throughout their life(see the high bone levels of almost all eagles examinedin this study) and a few in lethal quantities leading toacute lead poisoning (see table 1 and Bezzel and Fuumlnf-stuumlck 1995 Zechner et al 2005 Kenntner et al 2007)

Besides causing directmortality through the inges-tion of high amounts of lead the intake of sublethalamounts may affect avian populations by altering cog-nition and behaviour diminishing reproductive suc-cess and causing diseases as well as starvation ortraumatic events or by subjecting the exposed birds toundue predation (Gangoso et al 2009 Rodriguez-Ramos Fernandez et al 2011) The successive accumu-lation of larger sublethal quantities early in life mayindeed have resulted in a higher mortality (seefigure 2) However very little is known about theeffects of sublethal lead burdens in any wild bird

7

Environ Res Lett 10 (2015) 034003 MMMadry et al

population (Haig et al 2014) Although the goldeneagle population in the study area has increased in thelast 60 years (eg +10 since the census in 1990ndash1992Haller (1996)) and prosper at high density the intro-duction of lead-free ammunition for upland huntingin the investigated Alpine regionswould greatly reducethe overall lead burden and contribute to the health ofscavenging raptors in general This would be particu-larly important for bearded vultures which are beingre-introduced from captive breeding programs andstill represent a very small and vulnerable althoughincreasing population in the Alps (Schaub et al 2009)Their very high bone lead concentrations (see above)need further attention

Acknowledgments

We thank David Kistler (Swiss Federal Institute ofAquatic Science and Technology) for access to theMicrowave Digestion System Fabian von Kaenel forhis help with the ICP-MSmeasurements and RichardHoop (Institute of Veterinary Bacteriology Universityof Zurich) for the sampling of birds We thank theauthorities of the Cantonal Fish and Game Depart-ments and the many gamekeepers who helped collect-ing dead and moribund golden eagles and bonesamples of ibexes Werner Degonda performed theautopsies in Chur Veterinarians of the Universities ofBerne and Zurich provided additional data particu-larly Janne Schoumlning RomanMeier Ulrike Cyrus andJessica Gull Enrico Bassi from the Stelvio NationalPark and Daniel Hegglin Stiftung Pro Bartgeierprovided data from bones of bearded vultures Injuredor moribund birds were maintained in bird carestations by Christoph Meier Erich Widmer VreniMattmann and Andi Lischke Lorenzo VinciguerraUeli Schneppat and Reneacute Heim of the Natural HistoryMuseums of St Gallen Grisons and Lucerne preparedbone samples of some golden eagles and beardedvultures Marco Lanfranchi of the Department forNature and Environment of the Canton of Grisonsand Reto Giulio Meuli of the Swiss National SoilMonitoring Network (NABO) provided soil samplesHans Schmid Swiss Ornithological Institute helpedto coordinate the project Fraumlnzi Korner-NievergeltSwiss Ornithological Institute helped with data analy-sis and statistics

References

Bassi E and FerloniM2012 Lrsquoesposizione dei rapaci al piombo ilcaso della provincia di Sondrio Il PiomboNelleMunizioni daCaccia Problematiche e Possibili Soluzioni Rapporti ISPRA edAAndreotti and FBorghesi 53ndash4

Bassi E FerloniM andBianchi A 2013 Lrsquointossicazione da piombonei grandi rapaci necrofagi Info Gipeto 30 31

Bassi E FerloniMGugiatti A Pedrotti L Di GiancamilloMandGrilli G Il rischio di Saturnismo negli uccelli necrofagi inrelazione alle attualimodalitagrave di caccia degli ungulati AttiXVIConvegno Italiano diOrnitologia edRTinarelli

AAndreotti NBaccetti LMelega F Roscelli L Serra andMZenatelloAtti XVI Convegno Italiano diOrnitologia (inpress)

Bezzel E and FuumlnfstuumlckH J 1995Alpine SteinadlerAquila chrysaetosdurch Bleivergiftung gefaumlhrdet J Ornithol 136 294ndash6

Carpenter JW PatteeOH Fritts SH Rattner BAWiemeyer SNRoyle J A and SmithMR2003 Experimental lead poisoningin turkey vultures (Cathartes aura) JWildl Dis 39 96ndash104

Cerradelo SMunoz E To-Figueras JMateoR andGuitart R 1992Intoxicacion por ingestion de perdigones de plomo en dosaguilas realesDontildeana Acta Vertebrata 19 122ndash7

ChurchMEGwiazda R RisebroughRW SorensonKChamberlainCP Farry SHeinrichWRideout BA andSmithDR2006Ammunition is the principal source of leadaccumulated byCalifornia condors re-introduced to thewildEnviron Sci Technol 40 6143ndash50

ClarkA J and Scheuhammer AM2003 Lead poisoning in upland-foraging birds of prey in CanadaEcotoxicology 12 23ndash30

Craig THConnelly JWCraig EH and Parker T L 1990 Leadconcentrations in golden and bald eaglesWilson Bull 102130ndash3

Ethier A L Braune BM Scheuhammer AMandBondDE2007Comparison of lead residues among avian bonesEnvironPollut 145 915ndash9

FinkelsteinME et al 2010 Feather lead concentrations and207Pb206Pb ratios reveal lead exposure history of Californiacondors (Gymnogyps californianus)Environ Sci Technol 442639ndash47

Fisher I J PainD J andThomasVG2006A review of lead poisoningfrom ammunition sources in terrestrial birdsBiol Cons 131421ndash32

Franson J C Sileo L PatteeOHandMoore J F 1983 Effects ofchronic dietary lead in American kestrels (Falco sparverius)JWildl Dis 19 110ndash3

Gangoso L Alvarez-Lloret P Rodriacuteguez-Navarro AAMateoRHiraldo F andDonaacutezar J A 2009 Long-term effects of leadpoisoning on bonemineralization in vultures exposed toammunition sources Environ Pollut 157 569ndash74

Garcia-Fernandez A JMotas-GuzmanMNavas IMaria-Mojica PLunaA and Sanchez-Garcia J A 1997 Environmental expo-sure and distribution of lead in four species of raptors inSoutheastern SpainArch Environ Contam Toxicol 3376ndash82

GelmanACarlin J B SternH SDunsonDB Vehtari A andRubinDB 2014BayesianData Analysis 3rd edn (NewYorkCRCPress)

GelmanA andHill J 2007Data Analysis Using Regression andMultilevelHierarchicalModels (Cambridge CambridgeUni-verstiy Press)

Haig SMDrsquoElia J Eagles-SmithC Fait JMGervais J HerringGRivers JWand Schulz JH 2014The persistent problemof leadpoisoning in birds from ammunition and fishing tackleCondor 116 408ndash28

HallerH 1996Der Steinadler inGraubuumlnden Langfristige Untersu-chungen zur Populationsoumlkologie vonAquila chrysaetos imZentrumderAlpenOrnithol Beob Beiheft 9 1ndash168

Harmata AR andRestaniM2013 Leadmercury selenium andother trace elements in tisssue of golden eagles from South-westernMontana USA JWildl Dis 49 114ndash24

HuntG BurnhamW ParishCN BurnhamKKMutch B andOaks J L 2006 Bullet fragments in deer remains implicationsfor lead exposure in scavengersWildl Soc Bull 34 167ndash70

Kendall R J Lacher TE BunckCDaniel B Driver CGrueCELeighton F and StansleyW1996An ecological risk assessmentof lead shot exposure in non-waterfowl avian species uplandgame birds and raptorsEnviron Toxicol Chem 151 1ndash20

KenntnerN Crettenand Y FuumlnfstuumlckH J JanovskyMandTataruch F 2007 Lead poisoning and heavymetal exposure ofgolden eagles (Aquila chrysaetos) from the EuropeanAlpsJ Ornithol 148 173ndash7

Kramer J L andRedig PT 1997 Sixteen years of lead poisoning ineagles 1980ndash1995 an epizootiologic view J Raptor Res 31327ndash32

8

Environ Res Lett 10 (2015) 034003 MMMadry et al

to highly perfused organs First there is a rapidexchange between the circulating blood and theparenchyma of liver kidney and the brain (Namet al 2012) By replacement of calcium ions this heavymetal is then slowly transferred into the bones whichultimately contain gt90 of the overall body burdenWhereas lead in liver and kidney has a turnover rate ofweeks to months bones constitute a long-term depot(Ethier et al 2007 Rodriguez-Ramos Fernandezet al 2011) As a consequence lead levels in blood aremeasured for the diagnosis of poisoning in living birdswhereas analyses of liver and kidney are used for thepost-mortem confirmation (see table 1)

The concentrations of lead in the bones of raptorsare usually not directly related to current episodes ofexposure (Ethier et al 2007 Gangoso et al 2009) butcan increase rapidly after lead ingestion (Sandersonand Bellrose 1986) Concentrations gt10 μg gminus1 in

bone tissue are considered to be elevated and con-centrations gt20 μg gminus1 are often observed after lethalpoisoning (Mateo et al 2003 Rodriguez-Ramos Fer-nandez et al 2011) Interestingly the lead concentra-tions in the bones of golden eagles found in our study(median of 1245 μg gminus1 dry weight) were substantiallyhigher than those previously reported in the literaturefor the same species For example Mateo et al (2003)detected bone concentrations between 049 and497 μg gminus1 dry weight in golden eagles found in SpainWayland et al (1999) divided the birds into those withbackground hepatic lead levels (lt6 μg gminus1) and thosewith elevated hepatic levels (gt6 μg gminus1) Mean bonelead concentrations in this Canadian study were41 μg gminus1 for the former group and 97 μg gminus1 for thelatter Clark and Scheuhammer (2003) found inCanada that 5 out of 9 birds had bone lead concentra-tions gt675 μg gminus1 whereas we found in our study a

Figure 3Mean bone lead concentration of golden eagles and eagle owls comparedwith their prey Lines are 95 confidence intervals(if not shown they are smaller than the symbol)Means not sharing the same symbol are significantly different from each other at theplt 0001 level Numbers in parentheses are sample sizes

Figure 4Mean ratio of 207Pb208Pb and 206Pb208Pb found in bones of golden eagles eagle owls their prey and inAlpine ibex as wellas in ammunition and soil Ellipses are 95 confidence intervals A sample is significantly different from another sample if themean isnot includedwithin the 95 confidence ellipse of the other sample

6

Environ Res Lett 10 (2015) 034003 MMMadry et al

higher proportion (14 out of 17 specimens) with con-centrations in the bone gt675 μg gminus1

Other scavenging raptors are also likely to take uplead (see Rodriguez-Ramos Fernandez et al 2011)Among four examined bearded vultures from theAlps only one had a low lead concentration in bones(650 μg gminus1) while three had very high values(3890ndash10004 μg gminus1 Bassi et al (2013) Bassi et al inpress own unpublished data) Hence the bone leadconcentrations found in systematically collected deadgolden eagles in the eastern Swiss Alps was exception-ally high compared to those found in other goldeneagle populations In liver and kidney lead concentra-tions of golden eagles without signs of lead intoxica-tion did not exceed literature thresholds of elevatedlevels but were significantly higher than in eagle owlsHence although no signs of acute poisoning wereapparent even kidney and liver levels were elevatedcompared to another predator bird

Lead concentrations in bones of golden eagle preyanimals were gt10-fold lower than in golden eaglebones and ibex bones contained even gt20-fold lesslead (the median of 047 μg gminus1 found in this studycompares well with themedian of 059 μg gminus1 found byTataruch and Onderscheka (1995) in the same area)In contrast bones of eagle owl prey contained evenslightly more lead than eagle owl bones Therefore thelarge difference in bone lead concentration betweenthe two predators cannot be explained by differencesin lead concentration of their prey Part of the differ-ence between golden eagles and eagle owls in bone leadconcentration may be due to the fact that gastricpH values of owls are not quite as low as in raptors(Fisher et al 2006 Rodriguez-Ramos Fernandezet al 2011) and that owls regurgitate bones while rap-tors partly digest and partly regurgitate bones Hencethe absorption of ingested lead may be more completein raptors than in owls

The examination of lead isotope ratios revealedthat lead of golden eagles was most similar to that ofammunition used in the study area and differed fromthe isotope signature of golden eagle prey and soilsamples (even those with high lead concentrationsfrom ore mines or natural occurrence) Surprisinglythere was no change in isotope signature with increas-ing lead concentration in bones of golden eagles (orany other sample) This indicates that the source oflead ie from ammunition remains the same irre-spective of the amount of lead up-take

Taken together our findings indicate that lead ingolden eagles originates from ammunition and is notthe consequence of a bioaccumulation of genericallyavailable lead in the environment (eg from old oremine or aerial deposition of industrial lead) The find-ing that lead is accumulated in very high amounts inbones of golden eagles and is present in higheramounts than in another predator species even inliver and kidney suggests a frequent uptake of sub-lethal amounts of lead The lead concentration in

segments of wing feathers showed an irregular patternindicating an episodic rather than continuous leaduptake (ownunpublished data)

There are two main sources of ammunition leadfor golden eagles in the Alps which cannot be dis-tinguished by this study First golden eagles could feedon animals shot with lead pellets which were notretrieved or whose carcasses were left in the environ-ment (eg fox carcasses after skinning) Secondgolden eagles could take up lead fragments from ani-mals or their offal shot with lead bullets still themainammunition of hunters in the study area

When striking their targets conventional lead-based rifle bullets partly disintegrate intometallic frag-ments causing a widespread contamination of animaltissues (Church et al 2006 Hunt et al 2006 Bassi andFerloni 2012 Trinogga et al 2013 Haig et al 2014)Since golden eagles frequently prey upon weak mor-ibund or dead animals they undergo an increasedexposure to lead shot or bullet fragments enclosed inthe flesh of hunter-crippled game and prey carcassesIt is also general practice to eviscerate hunted wildlifein the field thereby leaving behind lead-contaminatedoffal (digestive tract heart lungs) that may be readilyingested by terrestrial raptors if not buried properlyDuring the hunting season about 10 000 shot reddeer roe deer chamois and ibex provide about 100tons of offal of which part may not be properly buriedand therefore available to the 120 breeding pairs ofgolden eagles in the Grisons The oral uptake of leadshot and bullet fragments from these sources maycause severe poisonings (Garcia-Fernandez et al 1997Pattee et al 2006 Stansley and Murphy 2011) Otherpossible routes of lead uptake seem much less likelyNonlethal lead shot at golden eagles and incorporatedinto the body has been found only in one case Leademissions during military exercises is not available tothe birds together with their food and are expected tocontribute minimally to the lead burden of goldeneagles

We conclude that in the Alps most golden eaglestake up lead from spent ammunition in carcasses ortheir offal in sublethal quantities throughout their life(see the high bone levels of almost all eagles examinedin this study) and a few in lethal quantities leading toacute lead poisoning (see table 1 and Bezzel and Fuumlnf-stuumlck 1995 Zechner et al 2005 Kenntner et al 2007)

Besides causing directmortality through the inges-tion of high amounts of lead the intake of sublethalamounts may affect avian populations by altering cog-nition and behaviour diminishing reproductive suc-cess and causing diseases as well as starvation ortraumatic events or by subjecting the exposed birds toundue predation (Gangoso et al 2009 Rodriguez-Ramos Fernandez et al 2011) The successive accumu-lation of larger sublethal quantities early in life mayindeed have resulted in a higher mortality (seefigure 2) However very little is known about theeffects of sublethal lead burdens in any wild bird

7

Environ Res Lett 10 (2015) 034003 MMMadry et al

population (Haig et al 2014) Although the goldeneagle population in the study area has increased in thelast 60 years (eg +10 since the census in 1990ndash1992Haller (1996)) and prosper at high density the intro-duction of lead-free ammunition for upland huntingin the investigated Alpine regionswould greatly reducethe overall lead burden and contribute to the health ofscavenging raptors in general This would be particu-larly important for bearded vultures which are beingre-introduced from captive breeding programs andstill represent a very small and vulnerable althoughincreasing population in the Alps (Schaub et al 2009)Their very high bone lead concentrations (see above)need further attention

Acknowledgments

We thank David Kistler (Swiss Federal Institute ofAquatic Science and Technology) for access to theMicrowave Digestion System Fabian von Kaenel forhis help with the ICP-MSmeasurements and RichardHoop (Institute of Veterinary Bacteriology Universityof Zurich) for the sampling of birds We thank theauthorities of the Cantonal Fish and Game Depart-ments and the many gamekeepers who helped collect-ing dead and moribund golden eagles and bonesamples of ibexes Werner Degonda performed theautopsies in Chur Veterinarians of the Universities ofBerne and Zurich provided additional data particu-larly Janne Schoumlning RomanMeier Ulrike Cyrus andJessica Gull Enrico Bassi from the Stelvio NationalPark and Daniel Hegglin Stiftung Pro Bartgeierprovided data from bones of bearded vultures Injuredor moribund birds were maintained in bird carestations by Christoph Meier Erich Widmer VreniMattmann and Andi Lischke Lorenzo VinciguerraUeli Schneppat and Reneacute Heim of the Natural HistoryMuseums of St Gallen Grisons and Lucerne preparedbone samples of some golden eagles and beardedvultures Marco Lanfranchi of the Department forNature and Environment of the Canton of Grisonsand Reto Giulio Meuli of the Swiss National SoilMonitoring Network (NABO) provided soil samplesHans Schmid Swiss Ornithological Institute helpedto coordinate the project Fraumlnzi Korner-NievergeltSwiss Ornithological Institute helped with data analy-sis and statistics

References

Bassi E and FerloniM2012 Lrsquoesposizione dei rapaci al piombo ilcaso della provincia di Sondrio Il PiomboNelleMunizioni daCaccia Problematiche e Possibili Soluzioni Rapporti ISPRA edAAndreotti and FBorghesi 53ndash4

Bassi E FerloniM andBianchi A 2013 Lrsquointossicazione da piombonei grandi rapaci necrofagi Info Gipeto 30 31

Bassi E FerloniMGugiatti A Pedrotti L Di GiancamilloMandGrilli G Il rischio di Saturnismo negli uccelli necrofagi inrelazione alle attualimodalitagrave di caccia degli ungulati AttiXVIConvegno Italiano diOrnitologia edRTinarelli

AAndreotti NBaccetti LMelega F Roscelli L Serra andMZenatelloAtti XVI Convegno Italiano diOrnitologia (inpress)

Bezzel E and FuumlnfstuumlckH J 1995Alpine SteinadlerAquila chrysaetosdurch Bleivergiftung gefaumlhrdet J Ornithol 136 294ndash6

Carpenter JW PatteeOH Fritts SH Rattner BAWiemeyer SNRoyle J A and SmithMR2003 Experimental lead poisoningin turkey vultures (Cathartes aura) JWildl Dis 39 96ndash104

Cerradelo SMunoz E To-Figueras JMateoR andGuitart R 1992Intoxicacion por ingestion de perdigones de plomo en dosaguilas realesDontildeana Acta Vertebrata 19 122ndash7

ChurchMEGwiazda R RisebroughRW SorensonKChamberlainCP Farry SHeinrichWRideout BA andSmithDR2006Ammunition is the principal source of leadaccumulated byCalifornia condors re-introduced to thewildEnviron Sci Technol 40 6143ndash50

ClarkA J and Scheuhammer AM2003 Lead poisoning in upland-foraging birds of prey in CanadaEcotoxicology 12 23ndash30

Craig THConnelly JWCraig EH and Parker T L 1990 Leadconcentrations in golden and bald eaglesWilson Bull 102130ndash3

Ethier A L Braune BM Scheuhammer AMandBondDE2007Comparison of lead residues among avian bonesEnvironPollut 145 915ndash9

FinkelsteinME et al 2010 Feather lead concentrations and207Pb206Pb ratios reveal lead exposure history of Californiacondors (Gymnogyps californianus)Environ Sci Technol 442639ndash47

Fisher I J PainD J andThomasVG2006A review of lead poisoningfrom ammunition sources in terrestrial birdsBiol Cons 131421ndash32

Franson J C Sileo L PatteeOHandMoore J F 1983 Effects ofchronic dietary lead in American kestrels (Falco sparverius)JWildl Dis 19 110ndash3

Gangoso L Alvarez-Lloret P Rodriacuteguez-Navarro AAMateoRHiraldo F andDonaacutezar J A 2009 Long-term effects of leadpoisoning on bonemineralization in vultures exposed toammunition sources Environ Pollut 157 569ndash74

Garcia-Fernandez A JMotas-GuzmanMNavas IMaria-Mojica PLunaA and Sanchez-Garcia J A 1997 Environmental expo-sure and distribution of lead in four species of raptors inSoutheastern SpainArch Environ Contam Toxicol 3376ndash82

GelmanACarlin J B SternH SDunsonDB Vehtari A andRubinDB 2014BayesianData Analysis 3rd edn (NewYorkCRCPress)

GelmanA andHill J 2007Data Analysis Using Regression andMultilevelHierarchicalModels (Cambridge CambridgeUni-verstiy Press)

Haig SMDrsquoElia J Eagles-SmithC Fait JMGervais J HerringGRivers JWand Schulz JH 2014The persistent problemof leadpoisoning in birds from ammunition and fishing tackleCondor 116 408ndash28

HallerH 1996Der Steinadler inGraubuumlnden Langfristige Untersu-chungen zur Populationsoumlkologie vonAquila chrysaetos imZentrumderAlpenOrnithol Beob Beiheft 9 1ndash168

Harmata AR andRestaniM2013 Leadmercury selenium andother trace elements in tisssue of golden eagles from South-westernMontana USA JWildl Dis 49 114ndash24

HuntG BurnhamW ParishCN BurnhamKKMutch B andOaks J L 2006 Bullet fragments in deer remains implicationsfor lead exposure in scavengersWildl Soc Bull 34 167ndash70

Kendall R J Lacher TE BunckCDaniel B Driver CGrueCELeighton F and StansleyW1996An ecological risk assessmentof lead shot exposure in non-waterfowl avian species uplandgame birds and raptorsEnviron Toxicol Chem 151 1ndash20

KenntnerN Crettenand Y FuumlnfstuumlckH J JanovskyMandTataruch F 2007 Lead poisoning and heavymetal exposure ofgolden eagles (Aquila chrysaetos) from the EuropeanAlpsJ Ornithol 148 173ndash7

Kramer J L andRedig PT 1997 Sixteen years of lead poisoning ineagles 1980ndash1995 an epizootiologic view J Raptor Res 31327ndash32

8

Environ Res Lett 10 (2015) 034003 MMMadry et al

higher proportion (14 out of 17 specimens) with con-centrations in the bone gt675 μg gminus1

Other scavenging raptors are also likely to take uplead (see Rodriguez-Ramos Fernandez et al 2011)Among four examined bearded vultures from theAlps only one had a low lead concentration in bones(650 μg gminus1) while three had very high values(3890ndash10004 μg gminus1 Bassi et al (2013) Bassi et al inpress own unpublished data) Hence the bone leadconcentrations found in systematically collected deadgolden eagles in the eastern Swiss Alps was exception-ally high compared to those found in other goldeneagle populations In liver and kidney lead concentra-tions of golden eagles without signs of lead intoxica-tion did not exceed literature thresholds of elevatedlevels but were significantly higher than in eagle owlsHence although no signs of acute poisoning wereapparent even kidney and liver levels were elevatedcompared to another predator bird

Lead concentrations in bones of golden eagle preyanimals were gt10-fold lower than in golden eaglebones and ibex bones contained even gt20-fold lesslead (the median of 047 μg gminus1 found in this studycompares well with themedian of 059 μg gminus1 found byTataruch and Onderscheka (1995) in the same area)In contrast bones of eagle owl prey contained evenslightly more lead than eagle owl bones Therefore thelarge difference in bone lead concentration betweenthe two predators cannot be explained by differencesin lead concentration of their prey Part of the differ-ence between golden eagles and eagle owls in bone leadconcentration may be due to the fact that gastricpH values of owls are not quite as low as in raptors(Fisher et al 2006 Rodriguez-Ramos Fernandezet al 2011) and that owls regurgitate bones while rap-tors partly digest and partly regurgitate bones Hencethe absorption of ingested lead may be more completein raptors than in owls

The examination of lead isotope ratios revealedthat lead of golden eagles was most similar to that ofammunition used in the study area and differed fromthe isotope signature of golden eagle prey and soilsamples (even those with high lead concentrationsfrom ore mines or natural occurrence) Surprisinglythere was no change in isotope signature with increas-ing lead concentration in bones of golden eagles (orany other sample) This indicates that the source oflead ie from ammunition remains the same irre-spective of the amount of lead up-take

Taken together our findings indicate that lead ingolden eagles originates from ammunition and is notthe consequence of a bioaccumulation of genericallyavailable lead in the environment (eg from old oremine or aerial deposition of industrial lead) The find-ing that lead is accumulated in very high amounts inbones of golden eagles and is present in higheramounts than in another predator species even inliver and kidney suggests a frequent uptake of sub-lethal amounts of lead The lead concentration in

segments of wing feathers showed an irregular patternindicating an episodic rather than continuous leaduptake (ownunpublished data)

There are two main sources of ammunition leadfor golden eagles in the Alps which cannot be dis-tinguished by this study First golden eagles could feedon animals shot with lead pellets which were notretrieved or whose carcasses were left in the environ-ment (eg fox carcasses after skinning) Secondgolden eagles could take up lead fragments from ani-mals or their offal shot with lead bullets still themainammunition of hunters in the study area

When striking their targets conventional lead-based rifle bullets partly disintegrate intometallic frag-ments causing a widespread contamination of animaltissues (Church et al 2006 Hunt et al 2006 Bassi andFerloni 2012 Trinogga et al 2013 Haig et al 2014)Since golden eagles frequently prey upon weak mor-ibund or dead animals they undergo an increasedexposure to lead shot or bullet fragments enclosed inthe flesh of hunter-crippled game and prey carcassesIt is also general practice to eviscerate hunted wildlifein the field thereby leaving behind lead-contaminatedoffal (digestive tract heart lungs) that may be readilyingested by terrestrial raptors if not buried properlyDuring the hunting season about 10 000 shot reddeer roe deer chamois and ibex provide about 100tons of offal of which part may not be properly buriedand therefore available to the 120 breeding pairs ofgolden eagles in the Grisons The oral uptake of leadshot and bullet fragments from these sources maycause severe poisonings (Garcia-Fernandez et al 1997Pattee et al 2006 Stansley and Murphy 2011) Otherpossible routes of lead uptake seem much less likelyNonlethal lead shot at golden eagles and incorporatedinto the body has been found only in one case Leademissions during military exercises is not available tothe birds together with their food and are expected tocontribute minimally to the lead burden of goldeneagles

We conclude that in the Alps most golden eaglestake up lead from spent ammunition in carcasses ortheir offal in sublethal quantities throughout their life(see the high bone levels of almost all eagles examinedin this study) and a few in lethal quantities leading toacute lead poisoning (see table 1 and Bezzel and Fuumlnf-stuumlck 1995 Zechner et al 2005 Kenntner et al 2007)

Besides causing directmortality through the inges-tion of high amounts of lead the intake of sublethalamounts may affect avian populations by altering cog-nition and behaviour diminishing reproductive suc-cess and causing diseases as well as starvation ortraumatic events or by subjecting the exposed birds toundue predation (Gangoso et al 2009 Rodriguez-Ramos Fernandez et al 2011) The successive accumu-lation of larger sublethal quantities early in life mayindeed have resulted in a higher mortality (seefigure 2) However very little is known about theeffects of sublethal lead burdens in any wild bird

7

Environ Res Lett 10 (2015) 034003 MMMadry et al

population (Haig et al 2014) Although the goldeneagle population in the study area has increased in thelast 60 years (eg +10 since the census in 1990ndash1992Haller (1996)) and prosper at high density the intro-duction of lead-free ammunition for upland huntingin the investigated Alpine regionswould greatly reducethe overall lead burden and contribute to the health ofscavenging raptors in general This would be particu-larly important for bearded vultures which are beingre-introduced from captive breeding programs andstill represent a very small and vulnerable althoughincreasing population in the Alps (Schaub et al 2009)Their very high bone lead concentrations (see above)need further attention

Acknowledgments

We thank David Kistler (Swiss Federal Institute ofAquatic Science and Technology) for access to theMicrowave Digestion System Fabian von Kaenel forhis help with the ICP-MSmeasurements and RichardHoop (Institute of Veterinary Bacteriology Universityof Zurich) for the sampling of birds We thank theauthorities of the Cantonal Fish and Game Depart-ments and the many gamekeepers who helped collect-ing dead and moribund golden eagles and bonesamples of ibexes Werner Degonda performed theautopsies in Chur Veterinarians of the Universities ofBerne and Zurich provided additional data particu-larly Janne Schoumlning RomanMeier Ulrike Cyrus andJessica Gull Enrico Bassi from the Stelvio NationalPark and Daniel Hegglin Stiftung Pro Bartgeierprovided data from bones of bearded vultures Injuredor moribund birds were maintained in bird carestations by Christoph Meier Erich Widmer VreniMattmann and Andi Lischke Lorenzo VinciguerraUeli Schneppat and Reneacute Heim of the Natural HistoryMuseums of St Gallen Grisons and Lucerne preparedbone samples of some golden eagles and beardedvultures Marco Lanfranchi of the Department forNature and Environment of the Canton of Grisonsand Reto Giulio Meuli of the Swiss National SoilMonitoring Network (NABO) provided soil samplesHans Schmid Swiss Ornithological Institute helpedto coordinate the project Fraumlnzi Korner-NievergeltSwiss Ornithological Institute helped with data analy-sis and statistics

References

Bassi E and FerloniM2012 Lrsquoesposizione dei rapaci al piombo ilcaso della provincia di Sondrio Il PiomboNelleMunizioni daCaccia Problematiche e Possibili Soluzioni Rapporti ISPRA edAAndreotti and FBorghesi 53ndash4

Bassi E FerloniM andBianchi A 2013 Lrsquointossicazione da piombonei grandi rapaci necrofagi Info Gipeto 30 31

Bassi E FerloniMGugiatti A Pedrotti L Di GiancamilloMandGrilli G Il rischio di Saturnismo negli uccelli necrofagi inrelazione alle attualimodalitagrave di caccia degli ungulati AttiXVIConvegno Italiano diOrnitologia edRTinarelli

AAndreotti NBaccetti LMelega F Roscelli L Serra andMZenatelloAtti XVI Convegno Italiano diOrnitologia (inpress)

Bezzel E and FuumlnfstuumlckH J 1995Alpine SteinadlerAquila chrysaetosdurch Bleivergiftung gefaumlhrdet J Ornithol 136 294ndash6

Carpenter JW PatteeOH Fritts SH Rattner BAWiemeyer SNRoyle J A and SmithMR2003 Experimental lead poisoningin turkey vultures (Cathartes aura) JWildl Dis 39 96ndash104

Cerradelo SMunoz E To-Figueras JMateoR andGuitart R 1992Intoxicacion por ingestion de perdigones de plomo en dosaguilas realesDontildeana Acta Vertebrata 19 122ndash7

ChurchMEGwiazda R RisebroughRW SorensonKChamberlainCP Farry SHeinrichWRideout BA andSmithDR2006Ammunition is the principal source of leadaccumulated byCalifornia condors re-introduced to thewildEnviron Sci Technol 40 6143ndash50

ClarkA J and Scheuhammer AM2003 Lead poisoning in upland-foraging birds of prey in CanadaEcotoxicology 12 23ndash30

Craig THConnelly JWCraig EH and Parker T L 1990 Leadconcentrations in golden and bald eaglesWilson Bull 102130ndash3

Ethier A L Braune BM Scheuhammer AMandBondDE2007Comparison of lead residues among avian bonesEnvironPollut 145 915ndash9

FinkelsteinME et al 2010 Feather lead concentrations and207Pb206Pb ratios reveal lead exposure history of Californiacondors (Gymnogyps californianus)Environ Sci Technol 442639ndash47

Fisher I J PainD J andThomasVG2006A review of lead poisoningfrom ammunition sources in terrestrial birdsBiol Cons 131421ndash32

Franson J C Sileo L PatteeOHandMoore J F 1983 Effects ofchronic dietary lead in American kestrels (Falco sparverius)JWildl Dis 19 110ndash3

Gangoso L Alvarez-Lloret P Rodriacuteguez-Navarro AAMateoRHiraldo F andDonaacutezar J A 2009 Long-term effects of leadpoisoning on bonemineralization in vultures exposed toammunition sources Environ Pollut 157 569ndash74

Garcia-Fernandez A JMotas-GuzmanMNavas IMaria-Mojica PLunaA and Sanchez-Garcia J A 1997 Environmental expo-sure and distribution of lead in four species of raptors inSoutheastern SpainArch Environ Contam Toxicol 3376ndash82

GelmanACarlin J B SternH SDunsonDB Vehtari A andRubinDB 2014BayesianData Analysis 3rd edn (NewYorkCRCPress)

GelmanA andHill J 2007Data Analysis Using Regression andMultilevelHierarchicalModels (Cambridge CambridgeUni-verstiy Press)

Haig SMDrsquoElia J Eagles-SmithC Fait JMGervais J HerringGRivers JWand Schulz JH 2014The persistent problemof leadpoisoning in birds from ammunition and fishing tackleCondor 116 408ndash28

HallerH 1996Der Steinadler inGraubuumlnden Langfristige Untersu-chungen zur Populationsoumlkologie vonAquila chrysaetos imZentrumderAlpenOrnithol Beob Beiheft 9 1ndash168

Harmata AR andRestaniM2013 Leadmercury selenium andother trace elements in tisssue of golden eagles from South-westernMontana USA JWildl Dis 49 114ndash24

HuntG BurnhamW ParishCN BurnhamKKMutch B andOaks J L 2006 Bullet fragments in deer remains implicationsfor lead exposure in scavengersWildl Soc Bull 34 167ndash70

Kendall R J Lacher TE BunckCDaniel B Driver CGrueCELeighton F and StansleyW1996An ecological risk assessmentof lead shot exposure in non-waterfowl avian species uplandgame birds and raptorsEnviron Toxicol Chem 151 1ndash20

KenntnerN Crettenand Y FuumlnfstuumlckH J JanovskyMandTataruch F 2007 Lead poisoning and heavymetal exposure ofgolden eagles (Aquila chrysaetos) from the EuropeanAlpsJ Ornithol 148 173ndash7

Kramer J L andRedig PT 1997 Sixteen years of lead poisoning ineagles 1980ndash1995 an epizootiologic view J Raptor Res 31327ndash32

8

Environ Res Lett 10 (2015) 034003 MMMadry et al

population (Haig et al 2014) Although the goldeneagle population in the study area has increased in thelast 60 years (eg +10 since the census in 1990ndash1992Haller (1996)) and prosper at high density the intro-duction of lead-free ammunition for upland huntingin the investigated Alpine regionswould greatly reducethe overall lead burden and contribute to the health ofscavenging raptors in general This would be particu-larly important for bearded vultures which are beingre-introduced from captive breeding programs andstill represent a very small and vulnerable althoughincreasing population in the Alps (Schaub et al 2009)Their very high bone lead concentrations (see above)need further attention

Acknowledgments

We thank David Kistler (Swiss Federal Institute ofAquatic Science and Technology) for access to theMicrowave Digestion System Fabian von Kaenel forhis help with the ICP-MSmeasurements and RichardHoop (Institute of Veterinary Bacteriology Universityof Zurich) for the sampling of birds We thank theauthorities of the Cantonal Fish and Game Depart-ments and the many gamekeepers who helped collect-ing dead and moribund golden eagles and bonesamples of ibexes Werner Degonda performed theautopsies in Chur Veterinarians of the Universities ofBerne and Zurich provided additional data particu-larly Janne Schoumlning RomanMeier Ulrike Cyrus andJessica Gull Enrico Bassi from the Stelvio NationalPark and Daniel Hegglin Stiftung Pro Bartgeierprovided data from bones of bearded vultures Injuredor moribund birds were maintained in bird carestations by Christoph Meier Erich Widmer VreniMattmann and Andi Lischke Lorenzo VinciguerraUeli Schneppat and Reneacute Heim of the Natural HistoryMuseums of St Gallen Grisons and Lucerne preparedbone samples of some golden eagles and beardedvultures Marco Lanfranchi of the Department forNature and Environment of the Canton of Grisonsand Reto Giulio Meuli of the Swiss National SoilMonitoring Network (NABO) provided soil samplesHans Schmid Swiss Ornithological Institute helpedto coordinate the project Fraumlnzi Korner-NievergeltSwiss Ornithological Institute helped with data analy-sis and statistics

References

Bassi E and FerloniM2012 Lrsquoesposizione dei rapaci al piombo ilcaso della provincia di Sondrio Il PiomboNelleMunizioni daCaccia Problematiche e Possibili Soluzioni Rapporti ISPRA edAAndreotti and FBorghesi 53ndash4

Bassi E FerloniM andBianchi A 2013 Lrsquointossicazione da piombonei grandi rapaci necrofagi Info Gipeto 30 31

Bassi E FerloniMGugiatti A Pedrotti L Di GiancamilloMandGrilli G Il rischio di Saturnismo negli uccelli necrofagi inrelazione alle attualimodalitagrave di caccia degli ungulati AttiXVIConvegno Italiano diOrnitologia edRTinarelli

AAndreotti NBaccetti LMelega F Roscelli L Serra andMZenatelloAtti XVI Convegno Italiano diOrnitologia (inpress)

Bezzel E and FuumlnfstuumlckH J 1995Alpine SteinadlerAquila chrysaetosdurch Bleivergiftung gefaumlhrdet J Ornithol 136 294ndash6

Carpenter JW PatteeOH Fritts SH Rattner BAWiemeyer SNRoyle J A and SmithMR2003 Experimental lead poisoningin turkey vultures (Cathartes aura) JWildl Dis 39 96ndash104

Cerradelo SMunoz E To-Figueras JMateoR andGuitart R 1992Intoxicacion por ingestion de perdigones de plomo en dosaguilas realesDontildeana Acta Vertebrata 19 122ndash7

ChurchMEGwiazda R RisebroughRW SorensonKChamberlainCP Farry SHeinrichWRideout BA andSmithDR2006Ammunition is the principal source of leadaccumulated byCalifornia condors re-introduced to thewildEnviron Sci Technol 40 6143ndash50

ClarkA J and Scheuhammer AM2003 Lead poisoning in upland-foraging birds of prey in CanadaEcotoxicology 12 23ndash30

Craig THConnelly JWCraig EH and Parker T L 1990 Leadconcentrations in golden and bald eaglesWilson Bull 102130ndash3

Ethier A L Braune BM Scheuhammer AMandBondDE2007Comparison of lead residues among avian bonesEnvironPollut 145 915ndash9

FinkelsteinME et al 2010 Feather lead concentrations and207Pb206Pb ratios reveal lead exposure history of Californiacondors (Gymnogyps californianus)Environ Sci Technol 442639ndash47

Fisher I J PainD J andThomasVG2006A review of lead poisoningfrom ammunition sources in terrestrial birdsBiol Cons 131421ndash32

Franson J C Sileo L PatteeOHandMoore J F 1983 Effects ofchronic dietary lead in American kestrels (Falco sparverius)JWildl Dis 19 110ndash3

Gangoso L Alvarez-Lloret P Rodriacuteguez-Navarro AAMateoRHiraldo F andDonaacutezar J A 2009 Long-term effects of leadpoisoning on bonemineralization in vultures exposed toammunition sources Environ Pollut 157 569ndash74

Garcia-Fernandez A JMotas-GuzmanMNavas IMaria-Mojica PLunaA and Sanchez-Garcia J A 1997 Environmental expo-sure and distribution of lead in four species of raptors inSoutheastern SpainArch Environ Contam Toxicol 3376ndash82

GelmanACarlin J B SternH SDunsonDB Vehtari A andRubinDB 2014BayesianData Analysis 3rd edn (NewYorkCRCPress)

GelmanA andHill J 2007Data Analysis Using Regression andMultilevelHierarchicalModels (Cambridge CambridgeUni-verstiy Press)

Haig SMDrsquoElia J Eagles-SmithC Fait JMGervais J HerringGRivers JWand Schulz JH 2014The persistent problemof leadpoisoning in birds from ammunition and fishing tackleCondor 116 408ndash28

HallerH 1996Der Steinadler inGraubuumlnden Langfristige Untersu-chungen zur Populationsoumlkologie vonAquila chrysaetos imZentrumderAlpenOrnithol Beob Beiheft 9 1ndash168

Harmata AR andRestaniM2013 Leadmercury selenium andother trace elements in tisssue of golden eagles from South-westernMontana USA JWildl Dis 49 114ndash24

HuntG BurnhamW ParishCN BurnhamKKMutch B andOaks J L 2006 Bullet fragments in deer remains implicationsfor lead exposure in scavengersWildl Soc Bull 34 167ndash70

Kendall R J Lacher TE BunckCDaniel B Driver CGrueCELeighton F and StansleyW1996An ecological risk assessmentof lead shot exposure in non-waterfowl avian species uplandgame birds and raptorsEnviron Toxicol Chem 151 1ndash20

KenntnerN Crettenand Y FuumlnfstuumlckH J JanovskyMandTataruch F 2007 Lead poisoning and heavymetal exposure ofgolden eagles (Aquila chrysaetos) from the EuropeanAlpsJ Ornithol 148 173ndash7

Kramer J L andRedig PT 1997 Sixteen years of lead poisoning ineagles 1980ndash1995 an epizootiologic view J Raptor Res 31327ndash32

8

Environ Res Lett 10 (2015) 034003 MMMadry et al

Lambertucci S ADonazagraver J AHuertas AD Jimeacutenez B SagraveezMSanchez-Zapata J A andHiraldo F 2011Widening theproblemof lead poisoning to a South-American top scaven-ger lead concentrations in feathers of wild Andean condorsBiol Cons 144 1464ndash71

Martin PA Campbell DHughes K andMcDaniel T 2008 Lead inthe tissues of terrestrial raptors in SouthernOntario Canada1995ndash2001 Sci Total Environ 391 96ndash103

Mateo R TaggartM andMeharg AA 2003 Lead and arsenic in bonesof birds of prey from SpainEnviron Pollut 126 107ndash14

Meuli RG Schwab PWaumlchterD andAmmann S 2014NationaleBodenbeobachtung (NABO) 1985ndash2004 Zustand undVer-aumlnderungen der anorganischen Schadstoffe und Bodenbegle-itparameter (Bundesamt fuumlrUmwelt Bern Umwelt-WissenNr 1409) pp 1ndash94

NamDH Rutkiewicz J and BasuN2012Multiplemetals exposureand neurotoxic risk in bald eagles (Haliaeetus leucocephalus)from twoGreat Lakes statesEnviron Toxicol Chem 31623ndash31

PainD J Fisher I J andThomasVG2009A global update of leadpoisoning in terrestrial birds from ammunition sourcesIngestion of Lead from Spent Ammunition Implications forWildlife andHumans edRTWatsonMFullerMPokras andWGHunt (Boise ID The Peregrine Fund) pp 99ndash118

PainD J Sears J andNewton I 1995 Lead concentrations in birds ofprey in BritainEnviron Pollut 87 173ndash80

PatteeOH Carpenter JW Fritts SH Rattner BAWiemeyer SNRoyle J A and SmithMR2006 Lead poisoning in captiveAndean condors (Vultur gryphus) JWildl Dis 42 772ndash9

RCore Team2014R A Language and Environment for StatisticalComputing (Vienna Austria R Foundation for StatisticalComputing)URL (wwwR-projectorg)

Rodriguez-Ramos Fernandez J HoumlfleUMateo RNicolas de FranciscoO Abbott R Acevedo P andBlanco JM

2011Assessment of lead exposure in Spanish imperial eagle(Aquila adalberti) from spent ammunition in central SpainEcotoxicology 20 670ndash81

SandersonGCandBellrose FC 1986AReview of the ProblemofLead Poisoning inWaterfowl IllinoisNaturalHistory SurveySpecial Publication 4 pp 1ndash31

SchaubM ZinkR BeissmannH Sarrazin F andArlettaz R 2009When to end releases in reintroduction programmes demo-graphic rates and population viability analysis of beardedvultures in theAlps J Appl Ecol 46 92ndash100

SpiegelhalterD ThomasA Best N and LunnD2007OpenBUGSUserManual Version 302 September 2007 (wwwmrc-bsucamacukbugs)

StansleyWandMurphy LA 2011 Liver lead concentrations inraptors inNew Jersey USA 2008ndash2010Bull EnvironContam Toxicol 87 171ndash4

Tataruch F andOnderschekaK 1995 Investigations on the heavymetal accumulation among ibex inGraubuumlndenZ Jagdwiss41 110ndash6

Trinogga A FritschGHoferH andKroneO 2013Are lead-freehunting rifle bullets as effective at killingwildlife as conven-tional lead bullets A comparison based onwound size andmorphology Sci Total Environ 443 226ndash32

Walker LA Chaplow J S Lawlor A J PereiraMG Potter EDSainsbury AWand Shore RF 2013 Lead (Pb) Concentrationsin Predatory Bird Livers 2010 and 2011 A Predatory BirdMonitoring Scheme (PBMS)ReportCentre for EcologyampHydrology Lancaster UKpp 1ndash12

WaylandMNeugebauer E andBollinger T 1999Concentrations oflead in liver kidney and bone of bald and golden eaglesArchEnviron Contam Toxicol 37 267ndash672

Zechner L Steineck T andTataruch F 2005 Bleivergiftung bei einemSteinadler (Aquila chrysaetos) in der SteiermarkEgretta 47157ndash8

9

Environ Res Lett 10 (2015) 034003 MMMadry et al