Náttúrufræðingurinn - 1990, Page 32

Tafla 1. Saga fálkaóðala þar sem kvenfuglar náðust oftar en einu sinni. Breeding status
of Gyrfalcon territories were females were captured in more than one year.
Óðal Territory Merki nr. Band no. 81 82 83 Ár Year 84 85 86 87 88
201 110164 X X Y X X X X —
207 17551 - X X X X X X -
206 112528 - - X X FD -
206 113484 - - X X X -
211 112525 - - - X - - -
211 110119 - - - X - - -
305 110118 - - - - X X X X
215 110117 - - - - X z z X
212 113489 __ _ _ _ _ — X X

Ath. X merkir að ungar hafi komist upp, ef undirstrikað að kvenfuglinn hafi náðst,
Y merkir að varp hafi misfarist, Z að kvenfuglinn hafi verið geldur og FD að fugl-
inn hafi fundist dauður. Note: X constitutes successful breeding, if underlined then
the female was captured that year, Y failed breeding, Z present and paired but not
breeding, and FD found dead.
SUMMARY
Age of first breeding and site
fidelity of Gyrfalcons
by
Ólafur K. Nielsen,
Maríubakki 26,
IS-109 REYKJAVÍK, Iceland
The author has been studying Gyrfal-
cons Falco rusticolus in NE Iceland since
1981 (for description of study area see
Nielsen and Cade 1990a). One part of this
project was to investigate mortality rates
of breeders by trapping at the same terri-
tories in successive years. Too few Gyrfal-
cons were captured to study survival of
adults but some information was gathered
on age of first breeding and site fidelity of
adults.
I trapped falcons during the breeding
season at active nests and caught 28 indi-
viduals, 22 females and 6 males. The fe-
males occupied 20 different territories. All
the males except one were paired to band-
ed females. Two females were caught in
two years, two were caught in three years
and one was caught in four years. This
gives a total of 37 captures. Four falcons,
two males and two females, had been
banded as nestlings on the study area.
One of these 28 birds was recovered dead
during the study.
The average weight of 28 females was
1830 g (standard deviation 102.7, range
1675-2020 g) and 5 males averaged 1355 g
(standard deviation 53.4, range 1300-1450
g). Most of the females were trapped 21-
35 days after initiation of laying. Three fe-
males trapped during the nesting period
(1675-1725 g) and one caught seven weeks
before laying (1750 g) were Iight com-
pared with females during the incubation
period (Fig. 1).
Both males banded as nestlings were
four years old when caught and both suc-
cessfully reared their broods. One of the
birds was trapped on a territory that had
been occupied by a successful breeding
pair in the previous year, so this bird
could have been breeding for the second
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