Breeding shearwaters on Italian islands: population size, island selection and co-existence with their main alien predator

Abstract

We review and update available information on the population size and distribution of Cory's Shearwater, Calonectris diomedea, and Yelkouan Shearwater, Puffinus yelkouan, in Italy. More than 90% of the population of these species rely on 64 islands, but the former breeds on twice as many islands as the latter. Some cases of local extinction were recorded. The analysis of distributions, along with that of island featu-res and presence of rats, showed inter-specific differences. The Yelkouan Shearwater tends to occupy larger and more offshore islands than the other species does. It's the only one that shows a clear positive correlation between abundance and island size. Finally, it is not present in rat-free islands, with a single exception of no quantitative relevance. Available data on the breeding success of both species are presented; comple-te failures where rats occur were recorded. Operations of rat control or eradication are presented and their consequences on seabirds' breeding success commented.

Full text

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* ISPRA (formerly INFS), via Ca’ Fornacetta 9, I-40064 Ozzano Emilia BO. E-mail: <nico-
la.baccetti@isprambiente.it>
** ARP Lazio, via del Pescaccio 96, I-00166 Rome RM
*** Gruppo Pontino Ricerche Ornitologiche, via Ticino 12, I-04100 Latina LT
*** Stazione d'Inanellamento c/o Dipartimento SENFIMIZO (Entomologia, Acarologia,
Zoologia), V.le Scienze, I-90128 Palermo PA
° Anthus snc, via Luigi Canepa 3, I-09129 Cagliari CA
°° AMP Tavolara - Punta Coda Cavallo, via Dante 1, I-07026 Olbia OT
°°° NEMO srl, Piazza D’Azeglio 11, I-50121 Firenze FI
Riv. ital. Orn., Milano, 78 (2): 83-100, 15-XI-2009
NICOLA BACCETTI*, DARIO CAPIZZI**, FERDINANDO CORBI***, BRUNO MASSA****,
SERGIO NISSARDI°, GIOVANNA SPANO°° & PAOLO SPOSIMO°°°
BREEDING SHEARWATERS ON ITALIAN ISLANDS:
POPULATION SIZE, ISLAND SELECTION AND CO-EXISTENCE
WITH THEIR MAIN ALIEN PREDATOR, THE BLACK RAT
Abstract – We review and update available information on the population size and
distribution of Cory’s Shearwater, Calonectris diomedea, and Yelkouan Shearwater,
Puffinus yelkouan, in Italy. More than 90% of the population of these species rely on 64
islands, but the former breeds on twice as many islands as the latter. Some cases of local
extinction were recorded. The analysis of distributions, along with that of island featu-
res and presence of rats, showed inter-specific differences. The Yelkouan Shearwater
tends to occupy larger and more offshore islands than the other species does. It’s the
only one that shows a clear positive correlation between abundance and island size.
Finally, it is not present in rat-free islands, with a single exception of no quantitative
relevance. Available data on the breeding success of both species are presented; comple-
te failures where rats occur were recorded. Operations of rat control or eradication are
presented and their consequences on seabirds’ breeding success commented.
Key words – Calonectris diomedea, Puffinus yelkouan, Rattus rattus, breeding
success, rat eradication, Italian islands.
Riassunto – Le berte nidificanti sulle isole italiane: popolazione, selezione delle
isole e convivenza con il principale predatore alloctono, il Ratto nero.
Viene presentata una revisione e un aggiornamento dei dati di popolazione e
distribuzione delle due specie di berte nidificanti in Italia. Più del 90% delle coppie di
entrambe risultano insediate su un totale di 64 isole, con la Berta maggiore presente
nel doppio di isole rispetto alla minore. Vengono documentati alcuni casi di estinzione
locale. L’analisi delle distribuzioni, a fronte delle caratteristiche dei siti e di dati sulla
presenza dei ratti, evidenzia differenze fra le due specie. La Berta minore tende ad
occupare isole mediamente più grandi e distanti da terra, è l’unica a mostrare una
chiara correlazione positiva tra abbondanza e ampiezza dell’isola, ed infine è in prati-

ca assente su tutte le isole prive di ratti. Vengono riuniti e commentati i dati disponi-
bili sul successo riproduttivo di entrambe le specie, comprensivi di casi di fallimento
totale su isole con presenza di ratti, nonché sulle conseguenze degli interventi finora
svolti di eradicazione e contenimento locale del predatore.
Parole chiave – Calonectris diomedea, Puffinus yelkouan, Rattus rattus, succes-
so riproduttivo, eradicazione dei ratti, isole italiane.
Introduction
Monitoring distribution and abundance of species is necessary for
determining conservation priorities, sound management strategies and
consequent actions (SUTHERLAND et alii, 2004; NICHOLS & WILLIAMS,
2006). The marine bird community of the Mediterranean, not particular-
ly rich in species but featured by a high level of endemism, has been
shaped by millennia of co-existence with man, which caused the lost of
many taxa since the very start of human history (ZOTIER et alii, 1999).
Not surprisingly, also in the present time, man-related threats to seabird
populations of this heavily developed sea basin represent a critical con-
servation issue, as shown by the contents of several single-species action
plans produced at a local or broader scale (e.g. GALLO-ORSI, 2003).
Knowledge on population size and distribution of Cory’s Shearwater,
Calonectris diomedea, and Yelkouan Shearwater, Puffinus yelkouan, has
improved within Italy in the course of the last decade only at a little
extent, despite their high conservation value. Two national overviews
dated c. 10 years apart (BRICHETTI et alii, 1992; BRICHETTI & FRACASSO,
2003) reported substantially the same data, except for slightly more pre-
cise information on minor colonies in the second report and a strongly
decreased estimate for the Yelkouan Shearwater in Sardinia. The lack of
new original information, leading to some sort of stagnation of knowledge
(the same population estimates being indefinitely re-proposed in time), as
well as the lack of island- or colony-based figures in the aforementioned
overviews, are the main reasons for the present paper, which is function-
al to identify management strategies and conservation priorities for these
two seabird species.
The black rat, Rattus rattus, is by far the most widespread terrestrial
mammal on the Mediterranean islands. It has been introduced in the
region by man two thousands years ago (AUDOIN-ROUZEAU & VIGNE, 1994;
MASSETI, 2008) and its detrimental impact on nesting seabirds has been
well documented in the last decades, at least at the local scale (e.g.
DAYCARD & THIBAULT, 1990; THIBAULT, 1995; PERFETTI et alii, 2001; IGUAL
et alii, 2006; PASCAL et alii, 2008; TRAVESET et alii, 2009). Among nesting
seabirds, shearwaters are especially vulnerable to rat predation upon
chicks and eggs (JONES et alii, 2008). Low impacts, however, have locally
84
BACCETTI, CAPIZZI, CORBI, MASSA, NISSARDI, SPANO & SPOSIMO

been assessed too (RUFFINO et alii, 2008) and a region-wide analysis failed
to identify the presence of rats as a factor conditioning shearwater distri-
bution and numbers (RUFFINO et alii, 2009).
We collected available population estimates and scattered breeding
records of shearwaters in Italy, at a geographical detail sufficient for
planning management strategies (particularly rat control and eradica-
tions) on the different islands. In addition, we performed ad hoc field
surveys on some islands lacking adequate coverage, this representing
the original part of our re-calculated totals. Geographic parameters,
black rat distribution and data on breeding success were analyzed in
order to understand present day distribution patterns. The operations
of rat removal and control that were so far carried out on Italian islands
occupied by shearwaters are reviewed.
Material and methods
The Italian ornithological literature was examined, searching for the
most recent information on local breeding records and colony size of the
two shearwater species. An island-based data bank, containing the best
and most recent population estimates and information on the presence
of black rats (and other predators) was created. The starting database
included 308 islands identified from satellite images and personal expe-
rience; rocks lacking any form of vascular vegetation were not consid-
ered, as they are usually unsuitable for breeding shearwaters. Sites
with unconfirmed or ‘probable’ breeding reports were not considered
either. Islands where shearwaters are known to have bred in the last
150 years, but not at present, appear in Appendix 1 with a zero popula-
tion size and a remark on local extinction. Abundances were in a few
cases (noted with an appropriate mark in Appendix 1) attributed from
vague original indications (e.g. ‘several’ pairs = 10-50) according to flex-
ible criteria, depending on the topographical context and the writer’s
particular terminology. Colonies repeatedly surveyed in time, or with
more than one population estimate available, were entered in the data-
base with the most recent figures. Values expressed by ranges (min.-
max., usually as a consequence of different assessing methods) were
transformed into geometric means for analysis and map production,
according to criteria adopted on large scale European assessments (cf
HAGEMEIJER & BLAIR, 1997; BIRDLIFE INTERNATIONAL, 2004). For the
islands inhabited by shearwaters, the flat surface area and distances
from the mainland and/or the nearest larger or comparable-sized island
were calculated. The Yelkouan Shearwater and Cory’s Shearwater are
indicated hereafter by the acronyms YS and CS, respectively. The pre-
liminary contents of our database data were previously made available
85
BREEDING SHEARWATERS ON ITALIAN ISLANDS

to BOURGEOIS & VIDAL (2008) for a global population assessment of YS,
and used by RUFFINO et alii (2009) for a broader scale analysis.
Differences in local estimates between the present paper and those
mentioned above are due to improved knowledge.
Results
With the only exception of three sectors of the Sardinian ‘mainland’
coast - Capo Caccia, Capo Figari and the Baunei cliffs - all the con-
firmed breeding records of the two shearwater species in Italy relate to
small islands, sized from 0.36 ha of South Paduleddi islet (near La
Maddalena, N Sardinia) to 8452 ha of Pantelleria island (cf dataset pre-
sented in Appendix 1). Very few of the smallest sized islands are occu-
pied, despite their high number, and the proportion of occupancy
increases with island size (Fig. 1). A total of only 64 islands out of 308
host (or hosted) at least one of the two shearwater species. From the
sum of min./max. local abundances, the population size of Italy amounts
to 3568-13212 YS pairs (sum of geometric means 6427) and 13344-
21873 CS pairs (sum of geometric means 15807). The mainland-breed-
ing fractions (Sardinia) of YS and CS amount, respectively, to 489 pairs
(7.1% of the national total) and 701 pairs (4.4%).
Local extinctions were recorded just in a single, probable case for CS
(Isola Rossa di Teulada in Sardinia, after 1901: cf LILFORD 1875 and
BONOMI 1901) and in at least two recent, confirmed cases for YS in
86
BACCETTI, CAPIZZI, CORBI, MASSA, NISSARDI, SPANO & SPOSIMO
Fig. 1 - Size of 308 Italian islands and frequency of occurrency of breeding shearwaters. The
most available size category (surface area <2 hectares) is nearly unexploited. Left y-axis: num-
ber of islands, right y-axis: shearwater occurrency (any species).

Tuscany: Pianosa after 1989 and Giannutri between 1993 and 2004 (see
Appendix 1 for details). Moreover, local extinction of YS is possible on
La Vacca and Cavoli islands in Sardinia, where night surveys are need-
ed to confirm current absence of calling individuals. At Palmaria island
in Liguria (not considered here for analysis and missing in Appendix 1),
YS might have got extinct already in pre-historical times as only sub-
fossil findings are known (BRICHETTI et alii, 1992). A careful search on
this island in 2005-2007 gave negative results on present occurrence
(M. Ferro and A. Peano, pers. comm.).
87
BREEDING SHEARWATERS ON ITALIAN ISLANDS
Fig. 2 - Distribution map of Calonectris diomedea in Italy. Circles: abundance on each island
(number of pairs, expressed by the geometric mean of max./min. estimates). Triangles: loca-
tion of the colonies on the Sardinian coast (irrespective of colony size).

The distribution maps of the two species, based on our database con-
tents, are shown in Figures 2 and 3. For YS, the largest population was
confirmed to be that of the Tavolara-Molara-Figarolo island complex,
with a new temptative estimate placed between 1510 pairs (preliminary
extrapolation from densities of occupied burrows in 2006 and 2007 on
the three islands) and 8500 pairs (corresponding to an evening count of
c. 17,000 incoming birds at two convenient sea-watching stations in
February 2008, i.e. just before egg-laying). For the largest CS colony
(Linosa island), the figure of 10,000 pairs is re-proposed; it had been
obtained in 1982 by capture-mark-recapture methods, by applying the
88
BACCETTI, CAPIZZI, CORBI, MASSA, NISSARDI, SPANO & SPOSIMO
Fig. 3 - Distribution map of Puffinus yelkouan in Italy. Circles: abundance on each island
(number of pairs, expressed by the geometric mean of max./min. estimates). Triangles: loca-
tion of the colonies on the Sardinian coast (irrespective of colony size).

Lincoln index (MASSA & LOVALVO, 1986) on the “Mannarazza” colony, by
far the largest on the island, but not the only one.
The number of islands inhabited by CS is just twice that of YS (58 vs
29, excluding mainland sites and Palmaria). The top sites for YS
(Tavolara) and CS (Linosa) hold 48% and 63% of the respective nation-
al populations. The much higher number of islands hosting CS is par-
alleled by a prevalence of relatively small settlements and a clearly
skewed distribution towards smaller-sized islands. Building the rank-
abundance curves of the log-transformed island population size of the
two shearwaters, the regression line is significantly steeper for YS (n= 29)
than it is for CS (n= 58) (ANCOVA, homogeneity of slopes test, F1, 84=9.94,
P<0.003, Fig. 4).
Island use by the two species suggests a different mechanism of site
selection. Within the subset of islands that hold shearwater colonies
(n=64), the number of YS pairs positively correlated with island surface
(Spearman’s R= 0.60, P<0.00001) and distance from closest island or
mainland (Rs= 0.37, P<0.003). No statistically significant relationship
were found for the abundance of CS with either island area (P>0.81) or
distance from closest island/mainland (P>0.64). There was a negative,
89
BREEDING SHEARWATERS ON ITALIAN ISLANDS
Fig 4 - Line plot showing the relation between log-transformed abundance of the two shear-
waters and the rank of the islands. The regression line is significantly steeper for YS (n= 29)
than it is for CS (n= 58) (ANCOVA, homogeneity of slopes test, P<0.003).

but not significant relationship between the numbers of pairs of the two
shearwaters (Rs= –0.17, P= 0.18, n= 64). Islands with colonies of CS
(n=58) have a smaller surface area and are closer to the mainland or
other islands than those with colonies of YS (n=29) (Mann-Whitney U
test: n=87, island area: adj. Z= 2.98, P<0.003; distance: adj. Z= 1.99,
P<0.05) and islands hosting both species (n=23) are larger and more dis-
tant from mainland or other islands than those with colonies of one
species only (n=41) (Mann-Whitney U test: n= 64, island area: adj.
Z= –3.49, P<0.0005; distance: adj. Z= –2.00, P<0.05).
Only on six of the 64 islands is the black rat absent (Toro and
Spargiotto in Sardinia, Lampione in Sicily and Argentarola, Cerboli,
Palmaiola in Tuscany). These rat-free islands have a max. surface area of
13 ha (Toro) and are significantly smaller than rat-inhabited islands
(Mann-Whitney U test: P<0.02, n= 64). Their distance from closest island
or mainland ranges between 483 m (Argentarola) and 18 km (Lampione).
Except for 1-2 YS pairs once found at Argentarola (0.02% of Italian popu-
lation), rat-free islands are occupied by CS only (total: 759-1395 pairs;
geometric mean: 1026, i.e. 6.5% of the Italian population). In two out of
these six sites, rats have been present during the past 25 to 50 years and
have naturally disappeared (Argentarola and Cerboli). Moreover, in order
to improve the breeding success of shearwaters, projects of rat eradica-
tion were carried out on La Scola (1.6 h., treated in winter 2000-01 and
again in 2005) and Giannutri (240 ha, winter 2005-06) in Tuscany and on
Zannone (105 ha, winter 2006-07) in Latium (PERFETTI et alii, 2001;
CAPIZZI et alii, 2007; SPOSIMO & BACCETTI, 2008; SPOSIMO et alii, 2008),
with an additional benefit for 1.3% of the CS national population. Rat
presence on islands that are not currently occupied by shearwaters is
incompletely known, nevertheless the ratio with/without rats within the
subsample of adequately assessed cases suggests that probably at least
85% of the 308 Italian islands host rats, the largest of the rat-free ones
being Mal di Ventre in Sardinia (87.9 ha).
The consequence of rat eradication determined in CS a sudden and
long lasting increase of productivity, from zero to 0.7-0.9 fledglings/pair,
as shown by regular monitoring at La Scola (Fig. 5, cf also SPOSIMO &
BACCETTI, 2008). Available information on the breeding success on some
Italian islands is summarized in Table 1, where higher values are appar-
ent for most rat-free islands and for islands where rats were even simply
controlled within the colony, and not eradicated. The local control of rats
within a colony site - but not in the rest of an island - has proven, there-
fore, to be highly beneficial, although on a temporary basis, and has been
instrumental to later achieve a full eradication (cf. also CORBI et alii,
2005b for Zannone island, before the eradication project was launched).
On Linosa, a local control of rats has been carried out in 2007-2008 in the
“Mannarazza” main CS colony. Breeding success of 39.4% in 2006, before
90
BACCETTI, CAPIZZI, CORBI, MASSA, NISSARDI, SPANO & SPOSIMO

91
BREEDING SHEARWATERS ON ITALIAN ISLANDS
Fig 5 - Breeding success of Calonectris diomedea on La Scola island, Tuscany (bars, left y-axis).
The line shows the number of burrows inspected twice per year (right y-axis). The first breed-
ing season after rats were eradicated was that of 2001. Toxic baits were used again when rats
returned in 2005.
Fig. 6 - Olive seeds regurgitated by Yellow-legged Gulls on La Vacca island and accumulated
by black rats under boulders in a colony of Calonectris diomedea. Olive fruits are collected by
gulls under plantations on the Sardinian mainland (photo: N. Baccetti, 2007).

the control started, increased in 2007 and 2008, after the rat control, to
89.3% (sample size: 150 nests) and 83.3% (sample size: 120 nests), respec-
tively. The high breeding success in 2007 suggested to extend the rat con-
trol area and in 2008 it covered also the “Scasciati” colony, where many
pairs of CS bred successfully (thick vegetation cover - including Opuntia
ficus-indica and Pistacia lentiscus prevented to estimate the breeding
success at this site). Not a single island holding YS had been treated up
to the 2008 breeding season, despite this species is only present on rat-
inhabited islands and it is heavily preyed upon by rats (e.g. 0% breeding
success on Molara and 23% on Tavolara, cf Tab. 1), with all successful
nests inside a few rat-free coastal caverns, i.e. in intra-island refuges
sensu RUFFINO et alii (2009).
92
BACCETTI, CAPIZZI, CORBI, MASSA, NISSARDI, SPANO & SPOSIMO
Island
Argentarola
(Tuscany)
La Scola
(Tuscany)
Cerboli
(Tuscany)
Zannone
(Latium)
San Domino
(Apulia)
Linosa
(Sicily)
Ponza
(Latium)
Molara
(Sardinia)
Tavolara
(Sardinia)
Island
area (ha)
1.2
1.8
8.8
104
208
545
750
347
600
Sp
CS
CS
CS
CS
CS
CS
CS
CS
CS
YS
YS
YS
YS
Rat
N
Y
Y
N
N
Y
C
C
C
Y
Y
C
C
Y
Y
Y
C
Y
Y
Y
N
Breeding
success
0:33
0.71
0.86
0
0
0.81
0.47
0
1:00
0.93
0.83
0.85
0.39
0.89
0.83
0
0.63
0.50
0.70
0
0
0
0.78
N
18
31
21
15
31
21
15
12
12
14
18
?
231
150
120
8
27
20
30
18
7
22
9
Year/remarks
1999
2000
2001
1989 (11 years before
rat eradication)
1999 (n= 9) and 2000 (n= 22): just
before rat eradication, see Fig. 5 for
subsequent variation
2000 (year with max. success)
2002 (year with min. success)
overall mean 1999, 2000,
2002, 2007: 0.69, n= 67
2003
2004
2005
2006
data from 1988-90
2006
2007
2008
2005
2006
2007
2008
2006
2007
2007 top of the island and
in caverns with rats
2007 inside caverns
inaccessible to rats
Reference
PERFETTI et alii 2001,
P. Sposimo & S. Romano,
unpubl. data
SPOSIMO & BACCETTI, 2008
PERFETTI et alii, 2001
PERFETTI et alii, 2001
P. Sposimo & F. Giannini
unpubl. data
CORBI et alii, 2005b,
F. Corbi & F. Pinos, unpubl. data
BRICHETTI & FRACASSO, 2003
RANNISI et alii, 2008
B. Massa,
unpubl. data
F. Corbi & F. Pinos,
unpubl. data
G. Spano & M. Putzu,
unpubl. data
Tab. 1 - Breeding success of shearwaters in relation to presence or absence
of Rattus rattus. Islands arranged according to surface area and species present
(CS Calonectris diomedea, YS Puffinus yelkouan). Presence of Rattus rattus (N = absent,
Y = present; C = locally controlled), number of fledged chicks/pair, number of sampled
nests and other remarks are also given.

Discussion
The insular breeding preference of shearwaters in Italy, as well as
across the rest of the Mediterranean (ZOTIER et alii, 1999), has probably
evolved in order to avoid terrestrial predators other than rats, which are
not a natural component of the local fauna. The three ‘mainland’ colonies
of Sardinia are lodged in vertical limestone cliffs with sea caves that are
not accessible to any terrestrial mammal either. Breeding in similar loca-
tions has been hypothesized for Sicily too, although it was never con-
firmed (cf. discussion in BRICHETTI, 1980) and appears most unlikely.
The national estimate of 3568-13212 YS pairs (sum of geometric
means 6427) is precedented by that of 11,000-18,000 by MESCHINI &
FRUGIS (1993), overestimated according to BRICHETTI & FRACASSO (2003)
who proposed 7000-14,000. The latter interval has also been accepted by
BIRDLIFE INTERNATIONAL (2004) and BOURGEOIS & VIDAL (2008); the sum of
local abundances listed by these authors, however, hardly reaches the
lower limit of the proposed intervals. These variations are mainly caused
by which figures are used for the Tavolara archipelago, where old Schenk’s
interval of 6000-9000 pairs, obtained back in 1978 (SCHENK & TORRE,
1986) and indefinitely reproposed in time (e.g. by referring it to 1995 in the
first IBA enquiry: GARIBOLDI et alii, 2000), was replaced in later IBA grey
literature (BRUNNER et alii, 2002) by the proposal of a new range of 1000-
2000 pairs in 1992-2001, without any given motivation or methodological
detail. The corresponding interval in our database, of 1510-8500 pairs, has
been obtained from independent and recent data and reproposes higher
values, but seems no less susceptible of further, major adjustments accord-
ing to improved knowledge from ongoing monitoring.
Our national estimate, updated to 2003-2008 for over 60% of the pop-
ulation, suggests for the YS a marked decrease (-54%) from the first
available figures of 1978-1985 (MESCHINI & FRUGIS, 1993). Previous
overestimation had been suggested as a cause for recently decreasing
the estimate (BRICHETTI & FRACASSO, 2003). However, vast abandoned
sectors of Tavolara colonies, decreased raft sizes and a breeding success
close to zero in most parts of the Tavolara archipelago suggest that a
strong population decline could indeed have occurred, confirming the
worst scenario of the 12-50% decrease proposed for the whole global
range (BOURGEOIS & VIDAL, 2008).
The national total of 13,344 - 21,873 pairs of CS (sum of geometric
means 15,807) is more in agreement with previous estimates of
MESCHINI & FRUGIS (1993), BRICHETTI & FRACASSO (2003), SULTANA &
BORG (2006) and BIRDLIFE INTERNATIONAL (2004), all reporting 15,000-
18,000 pairs. This is mainly due to the fact that the estimate for the
largest colony (Linosa, 63% of the Italian population) has remained
unchanged since a couple of decades.
93
BREEDING SHEARWATERS ON ITALIAN ISLANDS

Data on breeding success seem to confirm that CS is more vulnera-
ble to rats on small than on larger islands, as reported by MARTIN et alii
(2000). This probably results from a higher predator density and/or
higher prey vulnerability where nests are more concentrated and nest-
site choice not as wide as on large islands (cf also RUFFINO et alii, 2009).
Island selection by the two species and the respective number of occu-
pied islands suggest, however, a greater vulnerability of YS when com-
pared to CS, and the urgent need of conservation efforts. Only YS,
breeding on a smaller number of islands (none of them rat-free), shows
signs of population decline and definitely underwent to some local
extinctions over the last decades (also in adjacent Corsica: BOURGEOIS &
VIDAL, 2008). This is not surprising, considering that even the main
colonies seem to be featured by a very low productivity rate, similar to
that recorded for CS only at sites of secondary importance. What is sur-
prising is rather the opposite, that heavily predated colonies have per-
sisted until now, after many centuries of rat presence on most
Mediterranean islands. To explain this apparent paradox (cf RUFFINO et
alii, 2009), we suggest that rats, despite being present for many cen-
turies, may have recently and diffusely increased in number, making
predation episodes more frequent and impacting than earlier. The pop-
ulation increase and spread of the Yellow-legged Gull, Larus micha-
hellis, (associated to habitat alterations: BEAUBRUN, 1994; VIDAL et alii,
1998; FOGGI et alii, 2000) represents the only large ecological novelty of
the post-war decades on most islets within our study area, as well as
across the rest of N Mediterranean (cf population data in THIBAULT &
BONACCORSI, 1999; ARCAMONE et alii, 2001; CORBI et alii, 2005a; CADIOU
et alii, 2004; BACCETTI et alii, 2008). Increasing food resources are being
provided to rats by breeding gulls, either in the form of prey remains,
pellets, dead chicks etc, or indirectly, favouring nitrophilous and/or
invasive plant species that may also sustain large rat numbers
(CASSAING et alii, 2005). Nearly the whole food delivered by gulls origi-
nates outside the island areas where rats are confined (e.g. from rub-
bish tips, fishing vessels and agriculture lands) and represents a
reserve that rats can exploit also for several months after gull colonies
have been deserted. A notable example of a long lasting crop is the huge
number of olive seeds (Fig. 6), regurgitated on the bare rocks of most
islands and steadily gnawed by rats over a long period, in order to
exploit their carbohydrate- and fat-rich kernels (cf RINALDI et alii, 1994;
CASELLI et alii, 1995). High site fidelity and adult survival, both being a
life trait of many procellariids, would have eventually allowed shear-
waters to cope with high nest predation and continue occupying their
traditional colony sites until now, across a time span that has not
exceeded the order of a few decades.
94
BACCETTI, CAPIZZI, CORBI, MASSA, NISSARDI, SPANO & SPOSIMO

Acknowledgements - We thank all colleagues and friends mentioned in Appendix 1, who
made their population data and experience available or joined us in the field. Particular
thanks are due to Francesca Giannini, Max Putzu and Marco Zenatello. Mimmo Ferro and
Aldo Peano provided negative data from Palmaria island and helped in the field on Giannutri.
Caterina Azara, Tino Cerchi, Egidio Trainito and Mirko Ugo most frequently joined the sea-
watching sessions in NE Sardinia. Augusto Navone (AMP Tavolara) facilitated the fieldwork
on Tavolara archipelago. Antonio Cimato (CNR, Florence) commented and provided references
on the nutritional value of olive kernels for rats, and Barbara Lastrucci produced the distri-
bution maps.
REFERENCES
ARCAMONE E., BACCETTI N., LEONE L., MELEGA L., MESCHINI E. & SPOSIMO P., 2001 -
Consistenza ed evoluzione della popolazione di Gabbiano reale Larus cachinnans
michahellis nidificante nell’Arcipelago Toscano. In: TELLINI FLORENZANO G., BARBAGLI F.
& BACCETTI N. (a cura di). Atti XI Convegno Italiano di Ornitologia - Avocetta, 25: 142.
AUDOIN-ROUZEAU F. & VIGNE J.-D., 1994 - La colonisation de l’Europe par le rat noir (Rattus
rattus) - Revue de paléobiologie, 13: 125-145.
BACCETTI N., 1989 - Notizie sull’avifauna nidificante a Pianosa (Arcipelago Toscano) - Quad.
Mus. St. Nat. Livorno, 10: 77-90.
BACCETTI N., 1994 - Uccelli marini nidificanti sull’isola di Montecristo (Arcipelago Toscano) -
Quad. Mus. St. Nat. Livorno, 13: 23-29.
BACCETTI N., LEONE L. M. & SPOSIMO P., 2008 - Il gabbiano corso e il gabbiano reale
nell’Arcipelago Toscano: pochi dell’uno e troppi dell’altro. In: I Quaderni del parco,
Docum. Tecn., 1 “Progetto LIFE Natura, Isole di Toscana: nuove azioni per uccelli mari-
ni e habitat” - Parco Naz. Arcipelago Toscano, pp. 45-52.
BEAUBRUN P.C., 1994 - Controllo numerico di una specie in espansione: il Gabbiano reale Larus
cachinnans. In: MONBAILLIU X. & TORRE A., La gestione degli ambienti costieri e insu-
lari del Mediterraneo - Edizioni del Sole, Alghero, pp. 353-379.
BIRDLIFE INTERNATIONAL, 2004 - Birds in Europe. Population estimates, trends and conserva-
tion status. BirdLife Int. Ser. No. 12 - BirdLife International, Cambridge, UK.
BONOMI P., 1901 - Dalla Sardegna. Appunti d’escursioni - Avicula, 5: 59-64, 102-104, 154-155.
BOURGEOIS K. & VIDAL E., 2008 - The endemic Mediterranean yelkouan shearwater Puffinus
yelkouan: distribution, threats and a plea for more data - Oryx, 42: 187-194.
BRICHETTI P., 1980 - Distribuzione geografica degli uccelli nidificanti in Italia, Corsica e isole
Maltesi - Natura Bresciana, 16: 82-158.
BRICHETTI P. & F RACASSO G., 2003 - Ornitologia italiana. Vol. 1 - Gaviidae-Falconidae - Perdisa
Editore, Bologna.
BRICHETTI P., DEFRANCESCHI P. & BACCETTI N. (eds), 1992 - Fauna d’Italia. Aves I. Vol. 29 -
Calderini, Bologna.
BRUNNER A., CELADA C., ROSSI P. & G USTIN M., 2002 - Sviluppo di un sistema nazionale delle
ZPS sulla base della rete IBA (Important Bird Areas) - LIPU BirdLife, Unpublished
report.
CADIOU B., PONS J.M. & YÉSOU P. 2004 - Oiseaux marins nicheurs de France métropolitaine
(1960-2000) - Biotope ed.
CAPIZZI D., BACCETTI N., GIANNINI F., MUSCETTA G., PERFETTI A., SPOSIMO P., ZERUNIAN S., 2007
- Balancing costs against benefits of black rat management on Mediterranean islands -
Hystrix, Italian Journal of Mammalogy, (n.s), Suppl. 2007: 510.
CASELLI S., CATRAMBONE G., CIMATO A. & RINALDI L.M.R., 1995 - Carboidrati, lipidi e proteine
nella germinazione del seme di olivo. In: Atti Convegno “L’olivicoltura mediterranea:
stato e prospettive della coltura e della ricerca” - Rende (CS), 26-28 gennaio 1995, pp.
409-414.
CASSAING J., DERRÉ C., MOUSSA I., PARGHENTANIAN T., BOCHERENS H. & CHEYLAN G., 2005 - Le
régime alimentaire du rat noir Rattus rattus dans les îles d’Hyères analysé par la bio-
chimie isotopique et les contenus stomacaux - Sci. Rep. Port-Cros natl. Park, Fr., 21 :
89-115.
95
BREEDING SHEARWATERS ON ITALIAN ISLANDS

CESARACCIO G. & RACHELI G., 1993 - Caprera natura - Paolo Sorba Ed., La Maddalena.
CORBI F., FRANCESCATO S. & PINOS F., 2005a - Il Gabbiano reale nell’Isola di Zannone: consi-
stenza, trend, evoluzione spaziale ed aspetti bio-ecologici. In: ZERUNIAN S. (ed.),
Habitat, flora e fauna del Parco Nazionale del Circeo - Uff. Gestione Beni ex-ASFD di
Sabaudia. Parco Nazionale del Circeo, pp. 225-235.
CORBI F., FRANCESCATO S., PINOS F., BACCETTI N., CAPIZZI D., SPOSIMO P., FORCINA G. &
ZERUNIAN S. 2005b - Intervento di controllo del Ratto nero nell’isola di Zannone (PNC)
a tutela di una colonia di Berta maggiore. In: ZERUNIAN S. (ed.), Habitat, flora e fauna
del Parco Nazionale del Circeo - Uff. Gestione Beni ex-ASFD di Sabaudia. Parco
Nazionale del Circeo, pp. 245-252.
DAYCARD L. & THIBAULT J-C., 1990 - Gestion de la colonie de Puffin cendré (Calonectris dio-
medea) de l’Ile Lavezzi (Corse): une experience de dératisation - Trav. Sci. Nat. Reg.
Reserves Nat. Corse, 28: 55-71.
FAVERO L., 1968 - Berta minore (Puffinus anglorum yelkouan Acerbi) - Riv. ital. Orn., 38: 292.
FOGGI B., SIGNORINI M. A., GRIGIONI A. & CLAUSER M., 2000 - La vegetazione di alcuni isolotti
dell’Arcipelago Toscano - Fitosociologia 37: 69-91.
FOZZI A, PISU D. & TORRE A., 1998 - Rapporto sull’avifauna marina nidificante. Parco
Nazionale dell’Asinara. Parco Nazionale del’Arcipelago della Maddalena. Medmaravis
- ICRAM, rapporto non pubblicato.
GALLO-ORSI U., 2003 - Species actions plans for the conservation of seabirds in the
Mediterranean Sea: Audouin’s Gull, Balearic Shearwater and Mediterranean Shag -
Scientia Marina, 67: 47-55.
GARIBOLDI A., RIZZI V. & C ASALE F., 2000 - Aree importanti per l’avifauna in Italia - LIPU, Parma.
HAGEMEIJER W. J. M. & BLAIR M. J. (eds), 1997 - The EBCC Atlas of European Breeding Birds:
their distribution and abundance - T. & A. D. Poyser, London.
IGUAL J. M., FORERO M. G., GOMEZ T., ORUETA J. F. & ORO D., 2006 - Rat control and breeding
performance in Cory’s shearwater (Calonectris diomedea): effects of poisoning effort
and habitat features - Animal Conservation, 9: 59-65.
JONES H.P., TERSHY B.R., ZAVALETA E.S., CROLL D. A., KEITT B.S., FINKELSTEIN M.E. & HOWALD
G. R., 2008 - Severity of the Effects of Invasive Rats on Seabirds: A Global Review -
Conservation Biology, 22: 16-26.
LILFORD L., 1875 - Cruise of the Zara, RYS, in the Mediterranean - Ibis, 5: 1-35.
LILFORD L., 1887 - Notes on the Mediterranean Ornithology - Ibis, 19: 261-283.
MARTIN J.L., THIBAULT J.C. & BRETAGNOLLE V., 2000 - Black rats, island characteristics and
colonial nesting birds in the Mediterranean: consequences of an ancient introduction -
Conservation Biology, 14: 1452-1466.
MASSA B. & LOVALVO M., 1986 - Biometrical and biological considerations on the Cory’s
Shearwater Calonectris diomedea. In: MEDMARAVIS & MONBAILLIU X., Mediterranean
Marine Avifauna, pp. 293-313.
MASSETI M., 2008. Uomini e (non solo) topi: gli animali domestici e la fauna antropocora -
Firenze Univ. Press, Firenze.
MESCHINI E. & FRUGIS S., 1993 - Progetto Atlante degli uccelli nidificanti in Italia - Suppl. Ric.
Biol. Selvaggina, 20: 1-344.
MOCCI DEMARTIS A., 1986 - Seabirds of the Southern Sardinian island. In: MEDMARAVIS &
MONBAILLIU X. (eds), Mediterranean Marine Avifauna - NATO ASI Series. Vol. G12 -
Springer Verlag, Berlin, pp. 19-30.
NICHOLS J.D. & WILLIAMS B.K., 2006 - Monitoring for conservation - Trends Ecol. Evol., 21:
668-673.
PASCAL M., LORVELEC O., BRETAGNOLLE V. & C ULIOLI J.-M., 2008 - Improving the breeding suc-
cess of a colonial seabird: a cost-benefit comparison of the eradication and control of its
rat predator - Endang. Species Res., 4: 267-276.
PERFETTI A., SPOSIMO P. & B ACCETTI N., 2001 - Il controllo dei ratti per la conservazione degli uccel-
li marini nidificanti nelle isole italiane e mediterranee. In: TELLINI FLORENZANO G., BARBAGLI
F. & BACCETTI N. (a cura di). Atti XI Convegno Italiano di Ornitologia - Avocetta, 25: 126.
RABOUAM C., RIBEYRE J.P., SEGUIN J.F., THIBAULT J.C. & ZOTIER R., 1995 - Les oiseaux marins
reproducteurs des îles mineures de la Maddalena (Bouches de Bonifacio) - Travaux
scientifiques du Parc naturel régional et des réserves naturelles de Corse, 56: 71-81.
96
BACCETTI, CAPIZZI, CORBI, MASSA, NISSARDI, SPANO & SPOSIMO

RANNISI G., MURABITO L. & GUSTIN M., 2008 - Impact of predation by the Black Rat Rattus rat-
tus on the breeding success of Cory’s Shearwater Calonectris diomedea on Linosa Island
(Sicily, Italy) - Ornis Svecica, 18: 114-122.
RINALDI L.M.R., MENABENI D., LAMBARDI M. & CIMATO A., 1994 - Changes of carbohydrates in
olive seed (Olea europaea) during fruit maturation, and their correlation with germi-
nation - Acta Horticolturae, 356: 58-61.
RUFFINO L., BOURGEOIS K., VIDAL E., ICARD J., TORRE F. & LEGRAND J., 2008 - Introduced pred-
ators and cavity-nesting seabirds: unexpected low level of interaction at breeding sites
-Can. J. Zool., 86: 1068-1083.
RUFFINO L., BOURGEOIS K., VIDAL E., DUHEM C., PARACUELLOS M., ESCRIBANO F., SPOSIMO P. ,
BACCETTI N., PASCAL M. & ORO D., 2009 - Invasive rats and seabirds: a review after
2,000 years of an unwanted coexistence on Mediterranean islands - Biological
Invasions, 11: 1631-1651.
SCHENK H. & TORRE A., 1986 - Breeding distribution, numbers and conservation of seabirds in
Sardinia, 1978-85. In: MEDMARAVIS & MONBAILLIU X., (eds.). Mediterranean Marine
Avifauna. Population Studies and Conservation. NATO ASI Series. Vol. G12 - Springer
Verlag, Berlin, pp. 449-463.
SPOSIMO P. & B ACCETTI N., 2008 - La tutela della colonia di berta maggiore (Calonectris dio-
medea) dell’isolotto La Scola. I Quaderni del parco, Docum. Tecn., 1 “Progetto LIFE
Natura, Isole di Toscana: nuove azioni per uccelli marini e habitat” - Parco Naz.
Arcipelago Toscano, pp. 29-32.
SPOSIMO P., CAPIZZI D., GIANNINI F., GIUNTI M. & BACCETTI N., 2008 - L’eradicazione del ratto
nero (Rattus rattus) nell’isola di Giannutri. I Quaderni del parco, Docum. Tecn., 1
“Progetto LIFE Natura, Isole di Toscana: nuove azioni per uccelli marini e habitat” -
Parco Naz. Arcipelago Toscano, pp. 33-38.
SULTANA, J. & BORG, J. J. 2006a - Population ecology and conservation of the Cory’s
Shearwater (Calonectris diomedea). Proceedings of the first symposium on the
Mediterranean action plan for the conservation of marine and coastal birds - RAC/SPA,
Tunis, pp. 37-39.
SUTHERLAND W.J., PULLIN A.S., DOLMAN P.M. & KNIGHT T.M., 2001. The need for evidence-
based conservation - Trends Ecol. Evol., 19: 305-308.
TELLINI FLORENZANO G., ARCAMONE E., BACCETTI N., MESCHINI E. & SPOSIMO P. (eds.), 1997 -
Atlante degli uccelli nidificanti e svernanti in Toscana (1982-1992) - Quad. Mus. Stor.
Nat. Livorno, Monografie, 1: 1-415.
THIBAULT J.-C. 1995 - Effect of predation by the black rat Rattus rattus on the breeding suc-
cess of Cory’s Shearwater Calonectris diomedea in Corsica - Mar. Ornithol., 23: 1-10.
TOSCHI A., 1953 - Osservazioni ornitologiche nell’Isola di Giannutri - Ric. Zool. appl. Caccia,
22: 1-20.
TRAVESET A., NOGALES M., ALCOVER J.A., DELGADO J.D., LOPEZ-DARIAS M., GODOY D., IGUAL J.M.
& BOVER P., 2009 - A review of the effects of alien rodents in the Balearic (Western
Mediterranean Sea) and Canary Islands (Eastern Atlantic Ocean) - Biol. Invasions, 11:
1653-1670.
VIDAL E., MÉDAIL F., TATONI T., ROCHE P. & V IDAL P., 1998 - Impact of gull colonies on the flora
of the Riou Archipelago (Mediterranean Islands of south-east France) - Biol. Conserv.,
84: 235-243.
ZENATELLO M., ZUCCA C., NISSARDI S. & BACCETTI N., 2006 - Distribuzione di Berta maggiore e
Berta minore in Sardegna - On-line report, 5 pp (www.infs-acquatici.it/Documenti/ber-
tesardegna2006_31ago2006.pdf).
ZOTIER R., BRETAGNOLLE V. & THIBAULT J.-C., 1999 - Biogeography of the marine birds of a con-
fined sea, the Mediterranean - J. Biogeography, 26: 297-313.
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98
BACCETTI, CAPIZZI, CORBI, MASSA, NISSARDI, SPANO & SPOSIMO
Region Site (Island) Island distance from closest island man alien Puffinus Calonectris
area closest island or mainland predators yelkouan diomedea
(ha) or mainland (m)
Apulia CAPRARA 49,5 320 San Nicola s r - 100-160 (126.5)
Apulia SAN DOMINO 208,6 298 San Nicola p r 30-50 (38.7) 200-240 (219.1)
Apulia SAN NICOLA 46,2 320 Caprara p r 70-100 (83.7) -
Latium FARAGLIONE DI CALZONE MUTO 1,0 66 Ponza n none? - 1-5 (2.2)
Latium GAVI 18,1 136 Ponza s r - 5-10 (7.1)
Latium PALMAROLA 125,1 7300 Ponza s r, c? 10-30 (17.3) 100-150 (122.5)
Latium PONZA 750,8 5700 Zannone p r, c, d 10-30 (17.3) 60-100 (77.5)
Latium SANTO STEFANO PONZIANE 31,0 1400 Ventotene s r, c? 1-10 (3.2) 5-10 (7.1)
Latium VENTOTENE 143,6 1500 S. Stefano p r, c 10-30 (17.3) 25-40 (31.6)
Latium ZANNONE 104,7 5700 Ponza n r (erad.) 1-10 (3.2) 24-30 (26.8)
Sardinia (E) BAUNEI (coast) - - - - - 100-1000 (316.2) -
Sardinia (E) CAPO FIGARI (coast) - - - - - - 3-20 (7.8)
Sardinia (E) FIGAROLO 22,1 368 mainland n r 10-100 (31.6) 30-100 (54.8)
Sardinia (E) MOLARA 347,9 1400 Proratora n r 300-600 (424.3) -
Sardinia (E) TAVOLARA 602,0 1150 Reulino p r, c 1200-7800 (3059.4) 10-50 (22.4)
Sardinia (N) BARRETTINI 10,3 712 Corcelli n r - 50-100 (70.7)
Sardinia (N) BUDELLI 171,8 240 Carpa s r, c - 40-80 (56.6)
Sardinia (N) CAMERE E 4,8 128 Camere W n r - 40-60 (49.0)
Sardinia (N) CAMERE W 3,6 86 Soffi n r - 40-60 (49.0)
Sardinia (N) CAPRERA 1581,8 0 Maddalena p r, c, p - * 20-200 (63.2)
Sardinia (N) CARPA 0,4 193 Santa Maria n r - 80-120 (98.0)
Sardinia (N) CORCELLI 12,5 150 Piana di Corcelli n r - * 1-10 (3.2)
Sardinia (N) MADDALENA 2014,6 0 Caprera p r, c, p, w * 10-100a (31.6) * 1-50b (7.1)
Sardinia (N) MORTORIO 55,7 950 Camere E n r - 40-60 (49.0)
Sardinia (N) NIBANI EAST 3,5 5 Nibani W n r - 1-10 (3.2)
Sardinia (N) NIBANI NORTH 2,6 240 Nibani W n r - 1-10 (3.2)
Sardinia (N) NIBANI WEST 7,7 5 Nibani E n r - 1-10 (3.2)
Sardinia (N) PADULEDDI SOUTH 0,4 23 Paduleddi N n r - 1-5 (2.2)
Sardinia (N) PIANA DI CORCELLI 3,9 150 Corcelli n r - * 1-10 (3.2)
Sardinia (N) RAZZOLI 164,3 70 Santa Maria n r, c - 30-200 (77.5)
Sardinia (N) SANTA MARIA 186,4 70 Razzoli p r, c * 1-20 (4.5) 50-200 (100.0)
Sardinia (N) SOFFI 44,7 80 Camere W n r - 10-30 (17.3)
Sardinia (N) SPARGI 421,9 1600 Maddalena s r, c, p 10-20 (14.1) 90-150 (116.2)
Sardinia (N) SPARGIOTTO 10,1 685 Spargi n none - 120-180 (147.0)
Sardinia (SE) CAVOLI 42,1 708 mainland n r * 1-20a (4.5) 5-30b (12.2)
Sardinia (SE) SERPENTARA 31,3 3258 mainland n r 10-50 (22.4) -
Sardinia (SW) PAN DI ZUCCHERO 4,1 280 mainland n r - 300-400 (346.4)
Sardinia (SW) ROSSA DI TEULADA 10,5 693 mainland n r - * 1-50 (7.1)
Sardinia (SW) SAN PIETRO 5089,2 3779 mainland p r, c, dog 500 -
Sardinia (SW) TORO 13,4 7709 mainland n none - 500-1000 (707.1)
Sardinia (SW) VACCA 9,1 2838 mainland n r * 1-20a (4.5) 5-50b (15.8)
Sardinia (W) CAPO CACCIA (coast) - - - - - 150-200 (173.2) 300-1600 (692.8)
Sardinia (W) FORADADA 5,1 286 mainland n r - 50-200 (100.0)
Sardinia (W) PIANA DI ALGHERO 13,3 85 mainland n r - 100-200 (141.4)
Sicily (N) ALICUDI 509,0 15480 Filicudi p r - 9-12 (10.4)
Sicily (N) FAVIGNANA 2004,9 4040 Levanzo p r, c, d, h 2-20 (6.3) 20-50 (31.6)
Sicily (N) FILICUDI 936,0 15480 Alicudi p r - 2-20 (6.3)
Sicily (N) LEVANZO 585,8 4040 Favignana p r 100 20-50 (31.6)
Sicily (N) LIPARI 3766,4 890 Vulcano p r 2-20 (6.3) 2-20 (6.3)
Sicily (N) MARETTIMO 1224,1 15860 Favignana p r 20-50 (31.6) 20-50 (31.6)
Sicily (N) PANAREA 340,0 14054 Lipari p r - 2-20 (6.3)
Sicily (N) SALINA 2630,6 4370 Lipari p r 2-20 (6.3) 10
Sicily (N) USTICA 825,5 53266 mainland p r - 15-20 (17.3)
Sicily (N) VULCANO 2119,5 890 Lipari p r 2-20 (6.3) 3-6 (4.2)
Sicily (S) LAMPEDUSA 2059,6 43000 Linosa p r, c, d 500-1000 (707.1) 20-50 (31.6)
Sicily (S) LAMPIONE 4,7 18000 Lampedusa n none - 50-70 (59.2)
Sicily (S) LINOSA 545,1 43000 Lampedusa p r 2-20 (6.3) 10000
Sicily (S) PANTELLERIA 8452,3 70500 mainland p r, c, d 2-20 (6.3) 500-5000 (1581.1)
Tuscany ARGENTAROLA 1,2 439 mainland n none 1-2 (1.4) 35-50 (41.8)
Tuscany CAPRAIA 1926,6 27000 mainland p r, c, (d: erad.) 110-500 (234.5) -
Tuscany CERBOLI 8,8 6681 mainland n none - 50-85 (65.2)
Tuscany GIANNUTRI 239,5 11471 mainland p r (erad.) extinct 50-200 (100.0)
Tuscany ISOLOTTO D' ERCOLE 6,5 320 mainland n r (failed erad.) - 1-10 (3.2)
Tuscany LA SCOLA 1,6 242 Pianosa n r (erad.) - 60-100 (77.5)
Tuscany MONTECRISTO 1071,7 29410 Pianosa p r 400-750 (547.7) -
Tuscany PALMAIOLA 7,2 2950 Elba n r (erad.) - 4-10 (6.3)
Tuscany PIANOSA 1026,4 13300 Elba p r, c, h extinct 30-50 (38.7)
Appendix 1 - Italian islands holding breeding shearwaters and Sardinian 'mainland' coasts where breeding has
been documented (italic). Geographic data, presence of potential alien predators (r= black rat, c= feral cat, d=

99
BREEDING SHEARWATERS ON ITALIAN ISLANDS
year sources
c. 2000 BRICHETTI & FRACASSO (2003): general estimates for the three islands: YS 100-150 pairs, CS 300-400 pairs; subdivision criteria: P. Brichetti pers. comm.
Absence on fourth island (Pianosa) confirmed 2007 (G. Albanese, N. Baccetti, L. Melega)
c. 2000 BRICHETTI & FRACASSO (2003): general estimates for the three islands: YS 100-150 pairs, CS 300-400 pairs; subdivision criteria: P. Brichetti pers. comm.
Absence on fourth island (Pianosa) confirmed 2007 (G. Albanese, N. Baccetti, L. Melega)
c. 2000 BRICHETTI & FRACASSO (2003): general estimates for the three islands: YS 100-150 pairs, CS 300-400 pairs; subdivision criteria: P. Brichetti pers. comm.
Absence on fourth island (Pianosa) confirmed 2007 (G. Albanese, N. Baccetti, L. Melega)
2006 Own data (F. Corbi, F. Pinos, S. Francescato)
2005-2007 Own data (F. Corbi, F. Pinos, S. Francescato)
2005-2007 Own data (F. Corbi, F. Pinos)
2005-2007 Own data (F. Corbi, F. Pinos, S. Francescato)
2003-2004 Own data (F. Corbi, S. Francescato)
2005-2007 Own data (F. Corbi, F. Pinos, S. Francescato)
2005-2007 Own data (F. Corbi, F. Pinos, S. Francescato)
2006 Only this species has officially been given a confirmed breeding status (MESCHINI & FRUGIS, 1993; BRICHETTI & FRACASSO 2003). Population estimate sugge-
sted by an evening count of 1751 inds. from Punta Nera di Osalla in June 2006, cf. also ZENATELLO et alii, 2006; previous record: 31.03.1991, night calls heard
at Portu Pedrosu by S. Nissardi and P.F. Murgia). CS probably breeding too (ZENATELLO et alii, 2006)
2008 Own data (N. Baccetti, M. Putzu, G. Spano).
2006 Own data (N. Baccetti, M. Zenatello)
2006-07 Own data (N. Baccetti, M. Putzu, G. Spano).
2003-2008 Own data (cf. text; upper limit after subtraction of the Molara and Figarolo populations)
1998 FOZZI et alii, (1998); [RABOUAM et alii, (1995): 33-150 pairs].
1998 FOZZI et alii, (1998)
1998 FOZZI et alii, (1998)
1998 FOZZI et alii, (1998)
1992 CESARACCIO & RACHELI (1993); traditional exploiting of CS eggs. On adjacent Porco isl., (fresh?) eggshell fragments at burrow entrances in April, species unk-
nown (LILFORD, 1887).
1998 FOZZI et alii (1998); [RABOUAM et alii (1995): 16-40].
1995 RABOUAM et alii (1995)
(1992) a FAVERO (1968): exact location of breeding site not mentioned, possibly not this island; no recent confirmation; b CESARACCIO & RACHELI (1993); FOZZI et alii
(1993): confirmed breeding, no estimate given. Traditional exploiting of CS eggs reported by CESARACCIO & RACHELI (1993).
1991-1998 Own data (N. Baccetti); FOZZI et alii (1998): confirmed breeding, general estimate for all Arzachena islets 150-200 pairs.
1998 FOZZI et alii (1998): confirmed breeding, general estimate for all Arzachena islets 150-200 pairs. Apparently absent at present (own data, N. Baccetti & C.
Azara, June 2008).
1998 FOZZI et alii (1998): confirmed breeding, general estimate for all Arzachena islets 150-200 pairs. Apparently absent on an incomplete survey in June 2008
(M. Putzu & M. Zenatello pers. comm.)
1998 FOZZI et alii (1998): confirmed breeding, general estimate for all Arzachena islets 150-200 pairs. Own data: N. Baccetti, 2 empty nests 11/11/1986; C. Azara,
N. Baccetti, M. Putzu & M. Zenatello, 2 burrows not in use, apparently this species, June 2008, complete survey
1995 RABOUAM et alii (1995)
1995 RABOUAM et alii (1995)
1995 RABOUAM et alii (1995)
1995 RABOUAM et alii (1995)
1991-1998 Own data (N. Baccetti); FOZZI et alii (1998): confirmed breeding, general estimate for all Arzachena islets 150-200 pairs.
1998 FOZZI et alii (1998); [CESARACCIO & RACHELI (1993)]
1998 FOZZI et alii (1998); [RABOUAM et alii (1995): 50-100 pairs]
2007 a SCHENK & TORRE (1986): confirmed breeding record in 1976; MOCCI DEMARTIS (1986): questionable nest record in May 1982; apparently absent at present;
b Own data (N. Baccetti, S. Nissardi, M. Zenatello), June 2007
2008 Large number of un-occupied, long abandoned burrows. Own data: N. Baccetti, Serpentara isl., June 2008; S. Nissardi & M. Zenatello, empty nests, appa-
rently of Cory's Shearwater, on adjacent Varaglione Sud isl., June 2008
1997 Own data (N. Baccetti, S. Nissardi); [SCHENK & TORRE (1986)]
- Breeding first recorded by LILFORD (1875); BONOMI (1901): occupied burrows in April 1900; recent incomplete surveys suggest possible extinction: 2008, own
data (Baccetti, Nissardi, Zenatello)
1980 SCHENK & TORRE (1986)
2000 MARTIN et alii (2000); [SCHENK & TORRE, 1986: 300-400 pairs].
2007 a cf SCHENK & TORRE (1986), but breeding unlikely at present ; b Own data (N. Baccetti, M. Zenatello), June 2007; only previous report: LILFORD (1875), 12+ pairs
c. 2000 [SCHENK & TORRE (1986): 1500-2000 pairs], APLINGTON et alii (2000): CS 500-800 pairs, YS 150-200 pairs; both sources include Foradada isl. and Piana di
Alghero isl. in their estimates (separated here)
2000-2005 cf remark under Capo Caccia; own data (N. Baccetti)
1985-2000 cf remark under Capo Caccia; own data (N. Baccetti)
2007 Own data (B. Massa, P. Lo Cascio)
2005 Own data (B. Massa)
2006 Own data (B. Massa, P. Lo Cascio)
2005 Own data (B. Massa)
2006 Own data (B. Massa, P. Lo Cascio)
2006 Own data (B. Massa)
2006 Own data (B. Massa, P. Lo Cascio)
2007 Own data (B. Massa, P. Lo Cascio)
2006 Own data (B. Massa)
2007 Own data (B. Massa, P. Lo Cascio)
2007 Own data (B. Massa)
2005 Own data (B. Massa, P. Lo Cascio)
2007 Own data (B. Massa); CS eggs traditionally exploited until recently
2005 Own data (B. Massa)
2001 Own data (N. Baccetti, P. Sposimo)
2008 Own data (N. Baccetti, P. Sposimo); [TELLINI FLORENZANO et alii (1997)].
2007 Own data (P. Sposimo)
2005-2007 YS: large colonies (TOSCHI, 1953), >50 calling inds. (1986, Baccetti own data), >5 occupied burrows (1988-1993: A. Massi, M. Ferro pers. comm.), no contacts
(2005-07: P. Sposimo, N. Baccetti, own data). CS: (2005-07: P. Sposimo, N. Baccetti, own data)
c. 2005 M. Barlettani, pers. comm.
2007 Own data (N. Baccetti, P. Sposimo)
2007 A. De Faveri, B. Cursano, pers. comm.; [BACCETTI (1994): 50-250 pairs].
2001 Own data (N. Baccetti, P. Sposimo)
2007 Own data (N. Baccetti, P. Sposimo) [YS: BACCETTI, 1989]
feral dog, p= feral pigs or wild boars, w= weasel, h= hedgehog) and population estimates for both shearwater
species (range, followed by geometric mean, * = only order of magnitude known), years of reference of the estimate.