Fróðskaparrit - 01.01.2009, Blaðsíða 103

f EITT ÁR VÓRÐU REIÐURSTAÐIR HJÁ HAVHESTI (FULMARUS GLACIALIS) f FØROYUM
EYGLEIDDIR VIÐ VAKMYNDATÓLI
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the Faroes, adult fulmars were collected at
sea in 2003-2006 and examined with respect
to moulting status, showing that primary-
and tail moult occur from October to De-
cember (Danielsen et al„ unpubl.). This coin-
cides in time with the post-breeding disper-
sal of Faroese fulmars suggesting that they
might spend the moulting period in Faroese
offshore waters. However, virtually nothing
is known about the post-breeding dispersal
of the Faroese population and the origin of
the abovementioned fulmars collected for
moult studies is not known. Since the ful-
mars do not shed all primaries at the same
time they probably retain at least some fly-
ing ability (though see references in Bauer
and Glutz, 1966; Cramp, 1977; Huettmann
and Diamond, 2000:632 for somewhat con-
flicting views). Consequently fulmars are pre-
sumably able to travel some distance to ex-
ploit distant food resources. Although
primarily considered a plankton-feeder a
study of the species' diet in the Faroes has
shown that the fulmar is a flexible feeder and
that small-sized fishes of mesopelagic spe-
cies, notably the Glacier Lanternfish (Ben-
thosema glaciale), constitute an important
Part of the diet; though adult fulmars also
feed on other items such as cephalopoda,
planktonic crustacea (especially during bree-
ding season), and fish-offal (Danielsen et al.,
MS). The environmental conditions on the
Faroe shelf and in the offshore waters ensure
that rich food resources are available to the
Tiany species of seabirds that breed on the
islands (Salomonsen, 1955; Caard et al„
2002). While mesopelagic fish species pre-
sumably are available in autumn to fulmars
feeding in coastal waters the situation is dif-
ferent with regard to zooplankton. The
abundance of zooplankton is generally high
from late spring and through the summer
with a peak at the end of August and early
in September (coinciding with the main
fledging-period of young fulmars) and re-
mains at a relatively high level throughout
October (Gaard, 1999:Fig. 4). Around the
Faroes the dominating zooplankton is the
copepod Calanus finmarchicus, a large
species that probably constitutes most of the
significant volume of plankton found in the
stomachs of fulmars in spring and summer
(Danielsen et al„ MS), which in the autumn
occurs at greater depths (Gaard, pers. com.)
and thus is practically inaccessible to the ful-
mars. Whether the seasonal dynamics in the
abundance of zooplankton, or any food re-
source for that matter, is a key factor that de-
termines the post-breeding behaviourof the
Faroese fulmars is a subject for future stud-
ies. For instance, do the adults, despite a rel-
ative abundance of copepods, leave the
colony in order to reduce competition at a
time when there is a peak in number of
fledged young, or to exploit more distant
food resources? Because of great geographic
and seasonal variability of the marine envi-
ronments it has been suggested that seabirds
are capable of perceiving environmental cues
that may be used to predict future breeding
conditions (e.g. Cairns, 1987; Erikstad et al„
1998; Pinaud and Weimerskirch, 2002: Wan-
less et al„ 2007; though see Hipfner et al„
2008). For several colonial and other species
of birds prospecting behaviour during post-
breeding dispersal has been suggested as a
means of assessing the local habitat quality
and to assist in choosing suitable breeding
sites (e.g. Boulinier et al„ 1996; Doligez et al„
2002; Arlt and Párt, 2008), and it seems rea-