Fróðskaparrit - 01.01.2009, Blaðsíða 97

í EITTÁR VÓRÐU REIÐURSTAÐIR HJÁ HAVHESTI (FULMARUS GLACIALIS) f FØROYUM
EYGLEIDDIR VIÐ VAKMYNDATÓLI
95
breeding fulmars were captured by fleyg at
nests nos 1, 2, 3, 6, 9, 10, and 15, and fitted
with loggers in an eventually unsuccessful at-
tempt (the loggers were lost because the
birds abandoned their nests) to study forag-
ing movements.
Data storage and analyses
Recorded observations were tranfered on a
regular basis from the field computer to a
work computer for analysis on an 250GB ex-
ternal harddisc. In order to facilitate the
analyses the length of each recording was
maximized to 3-4 minutes, with an image of
what started it in a folder. As the purpose of
this paper is to examine nest-site attendance
on a year-round basis, and since both sexes
participate in parental care and thus are
present during both the incubation and
food provisioning periods, detailed data
from late May to early September have not
been included. The analysis of the data and
presentation of the results are divided into
two periods: first, the post-breeding period
from the birds' departure in September to
December when the fulmars usually make
their first landfall; secondly, the pre-breeding
period extending from January, when the ful-
mars begin to attend the colony on a more
regular basis, until late May when egg-laying
normally commences. Data from the pre-
breeding period were analysed on a monthly
basis, and attendance is expressed as percent
°f days that birds were present on the nest-
S|te. In order to examine to what extent the
male and the female simultaneously attend
the colony during the pre-breeding period,
and only seldom being able to make use of
the marked birds or video recordings to dis-
hnguish between the sexes, monthly atten-
dance was calculated for one (could be ei-
ther sex) and two (presumably male and fe-
male) birds separately. Since there were sta-
tistically no significant differences in
attendance between the nests the data were
pooled.
All statistical tests were done using SPSS
version 15 for Windows Vista and all data
were tested for homogeneity and normal
distribution.Test used were: ANOVA T-tests
and Mann-Whitney U-test. Only p-values for
two-tailed tests of significane are given.
Results
Breeding numbers and breeding succes
As shown in Table 2 the number of occupied,
potential nest-sites varied between 27 and
34 during the years of study, and the pro-
portion of active sites (i.e. where eggs were
laid) ranged from 25 to 38%. Altogether 18
of the 40 potential nest-sites were used for
breeding; 2 of them (nos 2 and 10) in all four
years, 5 in three years, 7 in two years, and 4
only once (Table 3). The number of fledged
young was 8 and 9 in 2004 and 2005, respec-
tively; but none in 2006 and only one in 2007
when, however, the fate of several eggs could
not be established. Most of the failures were
caused by abandonment at the egg stage (12
cases), though in 3 cases of egg predation
Hooded Crows (Coruus corone cornix) were
the culprits, working in pairs chasing off the
incubating fulmars, and once a Norwegian
rat (Rattus norvegicus) was video recorded
when instantly killing a half-grown chick.
Nest-site and mate fidelity
Only three (possibly 5) females and one male
of the adult fulmars (7 females and 3 males)
that were captured and ringed on nest-sites