Náttúrufræðingurinn - 1990, Side 33

A
N
0 1 2 3 4 5 km
iiiiiiii.il
6. mynd. Hreiðurstæði á fálkaóðali í
Suður-Þingeyjarsýslu. Óðalið er í árdal
og hreiðurklettarnir eru við ána. Ártöl
sýna hvenær fálkarnir notuðu viðko-
mandi hreiður. Engar upplýsingar eru
um ábúð 1977 og 1979. Kvenfugl 110164
var á þessu óðali 1981-87. Nest sites on
one Gyrfalcon territory in NE Iceland.
The territory is in a river valley and the
nesting cliffs follow the river. Years
when nest sites were occupied by breed-
ing falcons are indicated. No informa-
tion exists for 1977 and 1979. Female
110164 occupied this territory during
1981-87.
time on this territory. This male (Fig. 2)
was paired with an unbanded female in ju-
venile plumage (Fig. 3). The females were
two and three years old when captured,
and both successfully reared their broods.
The three years old female could have
been breeding for the second time on this
territory as it had been occupied by suc-
cessful pair the previous year (Fig. 4). The
males were 14 and 25 km from their natal
territories and the females 53 and 84 km.
Great variation in colouration of adults
was noted (Fig. 5).
These are the only recaptures known to
nte of Gyrfalcons banded as nestlings
caught breeding. Dementiew (1960) states
that Gyrfalcons breed in juvenile plumage
(one year old). I have observed ca. 250
successful breeding attempts on my study
area since 1981 and this is the second juve-
nile female I have seen breeding. Captive
Gyrfalcons, both sexes, have bred at the
age of four (Platt 1977).
All breeding females captured more
than once were recaught on their old terri-
tories but some at different nest sites.
Four females bred successfully in all years
they were known to occupy their territo-
ries but one female did not breed for two
years. Distance between nest sites varied;
one female was caught in three years in
the same nest, one moved 3.7 km between
years. The maximum distance between
different nest sites on the same territory
was 5.9 km (Fig. 6).
One female banded in 1983 was found
long-dead in July 1985 2 km from the nest
site. Her territory was occupied by a suc-
cessful pair from 1984 through 1987 when
the resident female was trapped. One fe-
male (two years old) produced young in
1984 but in 1985 she had been replaced.
Gyrfalcons are generally regarded as be-
ing faithful to their nesting territories (cf.
Palmer 1988). This is the first time this has
been confirmed with banded birds.
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