Fróðskaparrit - 01.01.2009, Blaðsíða 104

102
YEAR-ROUND VIDEO SURVEILLANCE OF INDIVIDUAL NEST-SITE
ATTENDANCE OF NORTHERN FULMARS IN THE FAROE ISLANDS
sonable to propose that this might also
apply to the Northern Fulmar.
Pre-breeding period
Several authors studying other species of
seabirds (viz. large gulls, kittiwakes, skuas,
and terns) have argued that early arrival
dates and high nest-site attendances are as-
sociated with strong intraspecific competion
for breeding sites, which also would prevent
„prospectors" from settling and breeding
(e.g. Wooller and Coulson, 1977; Duncan,
1978; Coulson, 1991; Klomp and Furness,
1992), or insufficient information about
breeding site and congeners, or simply a lack
of partner (Curio, 1982; Weimerskirch, 1992;
Ludwigs and Becker, 2002; Dittmann and
Becker, 2003). As to the Northern Fulmar, Sa-
lomonsen (1955) proposed that the early ar-
rival was due to intraspecific competion for
nest-sites and a relaxed interspecific com-
petion for food in winter. From a study in NE
Scotland, MacDonald (1980) concluded
that, although the nest-sites were defended
throughout the winter, there was no evi-
dence of intra- or interspecific competion for
nest-sites. Fisher (1952) compared observa-
tions from a large number of British breed-
ing-colonies and found a slightly earlier ar-
rivel at larger colonies than at smaller ones;
though he did not explicitly suggest any ex-
planation for this. The study colony at Sund
is a relatively small one (c. 30 pairs), and the
only other colony in the Faroes, for which
relevant, comparative data on post-breeding
absence exist (note that at Sund a sample of
nest-sites was studied), is the much larger
one (c. 200 pairs) in Kambsdalur, situated 19
km north of Sund and monitored for 12
years, where fulmars are to be seen in all
months of the year except for October
(Danielsen et al„ unpubl.). This is compara-
ble to observations at the similar-sized
colony at Marsden in Co. Durham, where the
fulmars were absent for only 3-4 weeks in
October and first days of November (Coul-
son and Horobin, 1972) and it is in agree-
ment with Fisher’s (1952) general observa-
tions on small versus large colonies in the
British Isles. Non-breeding fulmars, compris-
ing individuals that have not yet bred for the
first time and intermittent breeders (the two
categories are indistinguishable in the field),
usually constitute a considerable portion of
the adults in the colonies. At the Sund
colony this fraction was about two-thirds
while one-third has been recorded in other
studies (see Mallory and Forbes, 2007). Ring-
ing recoveries have shown that young birds
(pre-breeders) disperse more widely and are
less site faithful than fulmars that have bred
(Salomonsen, 1967; MacDonald, 1977c; Dun-
net et al„ 1979). It could be argued that
competition for nest-sites is stiffer in large
colonies than in smaller ones, and that pro-
specting pre-breeders therefore are either re-
pelled from, or attracted to smaller colonies,
which would also contribute to the colo-
nization of new breeding sites (Coulson and
Horobin, 1972). This would be consistent
with Fisher’s model for the timing of landfall
and an example (albeit selected!) in support
of the model is the island of Helgoland,
where the first prospecting fulmars appeared
in 1968, first successful breeding occurred
1972, and in the late 1970s the colony still
only comprised about a dozen pairs that de-
parted from the breeding grounds in August
and returned in late-February and in March
(Moritz, 1980). Possibly a two-step model