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Suppl . Ric. Bio l . Scìr . 'aggina XXVI (1997): 81-87

FRANCO CARPEGNA, FABRIZIO GRIECO, MARCELLO GRUSSU,EVA VE.RONESI, STEFANO VOLPONI

The Italian breeding population of Cormorant(Phalacrocorax, c arb o)

INTRODUCTION

In past centuries, the Cormorant in ltaly was known to breed both inwetlands, usual ly alongside herons, and on sea-cl i f fs (Salvadori , 1872).Breeding colonies on the mainland progressively disappearred during the lastcentLrry, but in Sardiniar four colonies were stil l present between 19ó5 and1975 (Baccett i & Brichett i , 1992; Schenk, 1976). Beginning in 1981, ar fewnest ing attempts have been recorded in north-eastern l taly, but the f i rstmainland colony weìs re-established in 198ó (Spina eî ol., 1986). At present,

the breeding range of the Cormorant in l tar ly comprises Sardinia, the Po

delta (NE l taly), and the Piedmont region (NW Italy) (Fig. 1). Occasionalb reed ing occ t t r red in 1990 and 1993 tn Lombardy (a long the Po r i ver ,Mantova province, and in fish ponds near the Adda river, Cremona plovin-

ce) , in 1992 in S ic i l y (Catan ia p rov ince) and in 1994 on the p la in nearBologna (Baccett i & Brichett i ,1992; Ciaccio, 1993; Tinarel l i , 1995).

RESULTS AND DISCUSSION

The I ta l ian breeding populat ion has been increasing s ince 1986 at a

mean annllal rate of 15,2o/o (from 1989 to 1995,7 coÌonies). The Piedmont

population has increased most rapidly (33,2ak,6 years, 1 colony), followed

82

;Fig. 1 - Locat ion ol thc I ta l ian cokrnics: sLluarL 's= r 'egular colonies; t l iangle 's= occasionzr l cokr-nic 's ; ?= blcccl ing at tcn-ìpts

by the Po Del ta populat ion (22,8a/o, 9 years, 5 colonies) . In contrast , thcSardinizrn population at S. Caterina di Pitt inuri is declining, probably becau-se of pcrsecr-rtion in r,vetlands ìn the northern Oristano Gr-rlf, the usual f 'ee-ding gror-rnd of these birds (Tab. 1).

Colonies are mainly locatecl in naturarl freshurater habitats (rivers arndestuaries) or artif icial ones (fishing ponds), rvhile only the Sardinian populer-tion nests on clifTs (Tab. 2). TI-re latter sitr-ration is rrery ir-rteresting, ars birdshave been considcrccl as belongir-rg to the sirzerzsls subspecies u,hicl-r r,rsuallvbr-eeds in inland habitats. On the mainland, either dezrd or l ivin.q trees are

I

Ét

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T. ' rn. 1 - Nurnbct o l 'p: r i ls Col t ' t rorant in I ta l izrn colontes

1 9 8 5 1 9 8 6 1 9 8 7 1 9 8 8 1 9 8 9 1 9 9 0 1 9 9 1 1 9 9 2 1 9 9 3 l 9 9 r + 1 9 9 - 5

Snn ta Ca te r - i na (OR)

Val Czrnrpot to (FE)

O lc l en i co (VC)

Val le tsc l t r rzz i (Fl l )

\ raÌ lc ' Mancl l io lc (RA)

P r rn t c A lbc re te r (RA)

C lo l na l c (AL )

Po l ivcr ' (Ml iJ)

La l i c o l Lcn t i n i (CT )

Ac l c l a l i v c r t Ze lbag l i a (CR)

N4a la l be l go (BO)

Total

? 33-36 ? 62-65 711 1 2 6 1 9 0 1 1 1

5

75 70-75 70-12 602t6 249 270 2802 1 3 2 ) 2 5 6

1 2 8 63

7 5t 8 09

:15

b 2639 8l o

I

2

45-48 ó I I 5 3 2 2 3 261 3 1 2 364 487 lrì7

T ,v ; . 2 - Hab i t a t i t nc l ncs t s i t c c l r a l z r c t c r - i s l i c s o f l t a l i an Co t ' n ro l i t n t co l o t r i c s , 1995

Santa Val OldenicoCatcrina Campotto

Vaìle Valle Punte CornaleBertuzzi Mandriolc Alberetc

I l a b i t a t

A l l i t t r c ì ea . s . l .

Sulrst latc

sca -c l i l l f i s ì r - ponds l i ve l ' Ì s l c trvr lclcl

4 0 l 0 1 4 0

rccl is c le i . rc l t lc lcs l iv i r rg t lces

b lac l< i s l r y>onc ì s , po r t c l s , t i v c t '

ìagoon rvet rr'<locls rrret l'oclcls sh<>t t:

I 1 | 1 2 0

cìcacì / l iv i : - rg t 'eecls l iv i l rg l iv ing

t lccs t leacl / l iv i r rg t rces 1 l 'ees t t cLìs

6 -12 0 -2 12 1 5 -20l l e i g l r t 0 - 1 0 , .5 - r - s l 0 -30

l lscc l as nest s i tes. ln the cokrnv o l 'Var l Canrpot to, avai labi l i tv of nest s i tes has

becn sl.r"onglv decrcasing dlrc tcl thc co.l lapsc clf ' I- looclecl cleacl trees. Hcre,

sonlc Cormor i ìnt pai t 's no\v ncst in l iv iug t rees oÌ l the banks o l -1hc pond, aucl

1 l-s11r patirs hervc sncccssfi-rl lv artten-rpted to breed in reecl stancls ch-rring thc

lzrst seasons. Nests ale usurail ly locetted u'ithin heror-iries, urith aissociatcd spe-

cics shou,r-r in tablc 3. Or-rlv at t l-re Verlle Mandriole color-rv clo Corrnoritnts

brcccl especiallv closc to othcr specics. The hcight of nests ab<x,e gt'ottncl or'

nrater-rernges fi-om 0 to 30 n-r. ln olcler-colclnies, nesl sites itre occltpiecl bcgin-

n ing f ' rc l r - t - r r - r - r ic l -Janr-rarv, ear l icr than i r - r the r rc t -v recent co lonics (Tnb.4) .

Cgìonv s ize is inc l icatcc l in tablc 1 bv the nrar imt tm nLtmber of occt tp icc l

nests recordccl ir-r ezich season. As a c<-rnsecll lcnce ol't l-rc lor-rg brcecling scitsoll,

at lcaist ir-r the colotl ies of northem ltltì1', some nest sites are occllpiecl mclre

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T're 3 - other colonizr l species obscn'ed breedir- rg cìose to Colmolants: I= ì r regglerr lv 6r 'occers icrnallv; R= regularll,.

Santa Val OldenicoCaterina Campotto

Valle Valle Punte CornaleBertuzzi Mandriole Alberete

Plt a la c rocorax o ri s t o I el i sPl t a la c roc o ra x p.r gt I t e t ! sN y c I i co ra r t t.\- c Í i c o ra rArdeoh ralloidesBtt lht rcus ib isEgrelta gdraettaEgretta olbÒArdea c:itrcreoArclea pttrpurertPIegadis lalcitreIIusP I a t a I e a I e t L c' o ro c I i r,t'l'

lt re s l< i o n t i s ct e I I t I o 7t i c. u sLants c:aclz int tans

T,re.4 - Phcnologv ancl bt 'crc 'c l ing success ar t l ta l iarr colonies, 199.5. , t Data f ì .orrr '1994.

RRRR R

IRRRR

RRR

[hern once pet: season; therefore, the total number of nest ing attempts isactlrally higher than the nraxinrum nLlmber of nests rccordecl (Grícco et al..1995).

The breedi'g success (Tab. a), in ternrs of numbcr of fleclglings per parir,appcars similar to other European popr-rlations. In two colonies, brecding o[i rrrmatl t re-plurnaged birds has rccent ly ta.ken place, includi lg imnratnresbreeding successfully together. In the north Italian colonies, regurlar breedilgby immature bircls Íì1ety sllggest a mechanism for population regr-rlation inwhich more bircls can breed in years and/or areas with high fo6ct ancl ncstavai labi l i ty. occurrence of breeding by i rnmature bircls is wel l known in

SantaCaterina

Val Oldenico ValleCampotto (") Bertuzzi

Valle Punte CornaleMandriole Alberete

Ear lv r - rc-sts

Mar n . nes t s

Last f lec lg ing

Seconcì brooclbchavior-u'

lnrm. brcccl ing

Brccding sLlcccss

rrricl .lan n r i c l Jan i a t e Ja r r m id Ma r . n t i c l Ma r . n r i d J r r r r Mav

I e t c M a r e u r ' l r M a t M i r r nr id Mav latc Ap| nr ic l Jr . rnnr id-Jun mic l Mav

lz i te Jul n ' r ic l Scp mic l Sep Ìate Sep ear lv Jt r l

uo ll aJ

) 4 ? R 2 , 7 1 6 2 , 0

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Europe, but not at many colonies, and immature breeders are known to herve

a lorv breeding success (Kort landt , 1942). Immatures are a lso knourn to

breed in large colonies l r ,h ich have reached the stabi l izat ion phase (T.

Bregnballe, pers. corîm.). We do not have any data about rccent changes in

food availabil itf in the habitats sLìrrounding colonies, but in thc Oldenico

and Val Campotto colonies fledgling production has not changed over the

last four vears. Hor,lever, the number of nesling attempts ol in-rmatr,rre birds

is negatively correlated rvith the avaiìabil ity of nest sites, and the decline of

the breeding population at VaÌ Campotto therefore may be due tnore to alai-

labil i ty of nest sites than iood supply.

In two colonies, the behaviour of some pairs late in the season suggests

that second broods could have occurred at least during years of strong popu-

lation grorvth as incr-rbating birds were observed alongside nests r,vith chicks

at the fledging stage (Grieco, 1994). Although birds nere not ir-rdividr-rzrÌÌv

marked, a lack of aggressiveness towards juveniles suggests thert some pairs

renested later in the season after a sllccessful attempt. The same behaviour

was observed in a ner,"ly-established colonv in France (Demongin, 1993). The

occurrence of second broods in nzrtural condition has beer-r recorded very

rarely in Europe (Crarnp and Simmons, 1977) and usually in associzrtion

rvith verr high lood levels. Recent records of second broods have been recor-

ded l ì 'on-r marked b i rds in large Danish coÌonies (T. Brcgnbal le , pers.

comm.). As u'ith age at f irst breeding, rearing second broods seems to be

commoner during the growth phase of the population. Further colour rin-

ging is required to determine the frequency of occurrence of doublc broo-

ding in relation to the stage of'colony establishment.

Recent changes in the arra i lab i l i ty of nest s i tes in t ree colonies cal lse

birds to respond in dil ' ferent \vzìys: (a) shift ing to sites of different strl lcture

and quality rvithin the colony area, such as reeds or broken trees; (b) lor-

ming nellr subcolonies outside thc original colon-y, i.e. in l iving trces on the

pond shore; (c) delaying breeding unti l nest sites are available: or' (d) migra-

ting to breed in nearbv colonies, which may have occLlrred ir-r some birds

fron-r Val Campotto.Courrts of ncsting pairs should be conducted carefully cspecially u,hen

breeding phenologv is protracted and re-nesting attempts occul-. At least one

count of occupied nests in early Merv and one in summer can estimale tl-re

number of nesting attempts to give a reliable index of population grourth.

Disturbance in most breeding colonies seerr- ts to be low or abscnt as

most colonies are rvithin nature reserves. Direct persecution r,r,as recorded

only at Val le Bcr tuzz i , one of only two unprotected colonies ( rv i th Santz i

Caterinzr).

86

According to the Habitat Evaìuation Procedure (Brichetti and Gariboldi,1992 & 1994), Cormorant scores a Total Standardized Vah-rc of 61.8, placir-rgi t 52nd on the I ta l ian l is t .

As statecl by other aruthors, due to isolartion, habitat characteristics andconsenrertion of biologiczrl divcrsity, the Sardiniar-r colony of Santa Caterinaidi Pitt inr-rri r,rr-gcntlv rcquires protection as a natl lre reserve.

. ACKNOWLE,DGEMb,NTS

Wc u' ish Lo Ll - ranh G. Alcsszrndl ia, A. Ci : rcc io, M. Del la Tof fo la, R. Gr- l rss l r ancl E. F]ol is u 'hol ' re lpecl in the f ie lchi 'o lk, ancl especi : r l l r ,Plo l ' . S. Frrreìs lb l i rc ìp l ì r l ac1r, icc.

S U M M A R Y

An ovct l icu ' o l thc Cort ' t . to latr t brccding colonies in l t : rh ' is presentecl . Ntrnrbels o l pai lsI ìunr 1985-1995 ale lepol tecl lor each bleecl i i ' r .s s i te- , u 'h i lc- c lctaì ls on habi tat , brcccl i r - rg beha-vior . r ls and bleecl ing success alc a lso plcscr . r tcc l . T l rc crrr rcnt populat ion s ize is nezr l l . , ,500 pzr i ls ,and thc iì\,cliìllc incrcase over- the l:rst 6 veals 15,2'2.

RIASSUNTO

La popolazione nidificante italiana di Cormorano (Phalacrocorar carbo)

Si prc-scnta una l is ionc conrplcssiva c lc l ìa p lesenza r ipnrdu{t i r . : r del Col lnorano in I la l ia,complct : r d i numcr i c l i coppie per-s i to (1985 1995) e c le l lagl i sr . r h i ib j tat , c . r .npol tan. ìcnto l ip lc . r -c l r - r t t ì r 'o e success() r ' ip loclLr t t i \ ,o (c lat i l i lc l i t i soplat tut to a l 199-5). I - : r popolazione coìr t i ì quasi 500coppir- , cc l c \ s tata calatLcl izzaLa da un incleme.nto mecl io c le l l5,2oi , negl i u l t i ln i 6 zrnni .

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