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Storm Petrels on a Mediterranean Island 127
five years later (on 14 July 1996), on a nest site at
Marettimo. This demonstrates a certain gene
flow between different colonies of the
Mediterranean. Also one individual ringed as a
chick at Marettimo on 16July 1994 was recovered
on 10 October 1994 at Skikda (Algeria, 37°N,
6°34'E, about 500kms to the SW).
We detected site tenacity of breeding birds
within different sectors of the cave. Table 3 shows
the total number and percentage of adults
ringed in each sector and recovered in the same
or in a different sector of the cave; the majority
of adults (88 out of 107 checked, 82.2%) were
recovered in the same nest where they had been
ringed. We also observed nest-site fidelity of
individuals to the sector of the cave and to sites
close to where they were ringed as chicks (17 of
Downloaded by [31.185.98.131] at 13:16 23 June 2016 23 chicks recovered, all brooding egg: Table 4).
Individuals ringed as chicks were recovered
as breeding adults, one (4 ind.), two (4 ind.), three
(4 ind.), four (7 ind.), five (9 ind.), six (1 ind.) and C
seven (2 ind.) years after fledging (Table 2).
DISCUSSION
The Storm Petrel is a long-lived bird, its
maximum life expectancy being between 20 and
32 years (Cramp & Simmons 1977; Riddington,
pers comm); its maturity and first breeding occur
generally between four and five years after
fledging. Mediterranean populations winter
within the Mediterranean basin; the habit of
wintering locally may affect vulnerability to
abiotic factors and thus mortality. During eleven
seasons of our research we recovered a modest
percentage of adults, and recovered no adults
more than six years after ringing, nor individuals
ringed as chicks aged more than seven years.
We also observed the existence of site fidelity
both of adults and chicks. Other Mediterranean
data on this species (Sultana & Borg (in press),
who have ringed for 30 years at Filfla Is.) confirm
the species' site fidelity and suggest a maximum
longevity of 20 years. One explanation of our
results may be a lower life expectancy in
Mediterranean populations compared to Atlantic
ones, bringing about high population turnover
and first breeding at a very young age. This
means that the mean age of individuals in
colonies should be low and intra-populational
turnover high.
© 2000 British Trust for Ornithology, Ringing & Migration, 20, 125-128
Table 3. Site fidelity of adults: number (and percentage)
of individuals ringed and recovered in the four sectors
(A-D) of the cave.
A B CD
A7 3 4
B4 10 1
C2 1 47 2
D 2 24
Table 4. Site fidelity of Storm Petrels ringed as chicks:
number of individuals ringed and recovered in the same
or different sector (A-D) of the cave.
ABCD
A3 7 1
B 2 1
21
D
5
With regard to conservation implications,
Tucker & Heath (1994) include the Storm Petrel
in the SPEC2 category and treat it as localized;
on the basis of our data and those reported by
other authors above quoted, the Mediterranean
population has to be considered in the vulnerable
status and in moderate decline. Preventing or
minimizing human disturbance at breeding
colonies during the nesting season is therefore
very important.
ACKNOWLEDGEMENTS
We thank R. Riddington very much for his useful
comments on a first draft of this paper; we are
also grateful to Adelaide Catalisano, Gabriella
Lo Verde and Leonardo Parisi for their assistance
during the study.
REFERENCES
Catalisano, A., Lo Valvo, F., Lo Verde, G. & Massa,
B. (1988) Dati biometrici sull'Uccello delle
tempeste (Hydrobates pelagicus). Atti IV Conv. ital.
Orn., Naturalista siciliano, 12 (suppl.), 261-265.
Cramp, S. & Simmons, K.E.L. (1977) The Birds of the
Western Palearctic. Vol. I. Oxford University Press.