Fróðskaparrit - 01.01.2009, Blaðsíða 105

í EITT ÁR VÓRÐU REIÐURSTAÐIR HJÁ HAVHESTI (FULMARUS CLACIALIS) í FØROYUM
EYCLEIDDIR VIÐ VAKMYNDATÓLI
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could be applicable, where some prospec-
tors are first attracted to a relatively old and
large colony but due to competition go else-
where (see also Coulson and Horobin, 1972).
However, the surveillance cameras did not
record any behaviours that indicated com-
petition for nest-sites (no other cliff-breed-
ing species nested within the colony area),
which of course could be due to the fact that
the colony was small. For the Northern Ful-
mar, and other long-lived seabird species,
prospecting for information regarding suit-
able feeding areas, breeding colonies, nest-
sites, and breeding success of conspecifics
(the „public information" hypothesis) is
probably a significant element of the species'
life-history strategy (see Forbes and Kaiser,
1994). MacDonald (1980) suggested that
breeding adults and other potential recruits
might use the „winter assembly" to look for,
and form pair-bonds with unmated birds. Al-
though the divorce and mortality rates
among fulmars are low, approximately 5% of
the breeders will lose their mates annually
and therefore have to search for a new part-
ner (MacDonald, 1977a; Ollason and Dun-
net, 1978). Despite scanty data, the present
study indicates that divorce rate may have
been higher and nest-site fidelty lower at
Sund (see Results and Table 4) than previ-
ously reported for other colonies, (Ollason
and Dunnet, 1978,1988). This may be due to
disturbance and a subsequent low breeding
success (Table 3) or some other environ-
mental unpredictability. In the context of
the „success-stay/failure-leave" concept
(Schmidt, 2004), breeding performance is
thought to influence both mate and site fi-
delity in long-lived seabirds (Naves et al„
2006); though with regard to site fidelity the-
ory predicts that it should be inversely re-
lated to lifespan and that individuals should
be site-faithful in unpredictable habitats pro-
vided there is equal site-quality (Switzer,
1993, 1997). However, not surprisingly in
view of the small sample-size, no significant
differences in first arrival dates and atten-
dance patterns between nest-sites and years,
or between successful and failed breeders,
are discernible in the present data (Table 5).
Almost invariably the first landfall occurred
in December though the attendance at the
individual nest-sites varied considerably
from a single day (and one minute to an
hour) to 9-10 days (Table 5). The fulmars
continued to visit the nest-sites intermit-
tently and with two individuals present
throughout the months January-March and
with two-bird-attendance reachinga peak in
April (Fig. 1); thus coinciding with the period
when all copulations were recorded (Table
6).
According to Hatch (1987a) fulmars
copulate only at the nest-site and in his stud-
ies of the species in Alaska, the pairs began
to copulate immediately upon first landfall
(c. 50 days prior to first eggs) and on average
every 2-4 hours in daylight. Furthermore, the
frequency of copulations peaked about 3
weeks before the egg is laid and the female is
inseminated 30-40 times before she departs
for the pre-laying exodus (Hatch, 1987a).
This is in sharp contrast to our study where
all copulations recorded by the cameras took
place during a relatively short period (11
April to 1 May), although the birds had been
attending the colony since in December or
January. In a study of albatrosses 96% of the
observed copulations occurred in one day
(Astheimer etal., 1985). In our fulmarcolony