Náttúrufræðingurinn - 2002, Blaðsíða 7

Tímarit Hins íslenska náttúrufræðifélags
Þessar athuganir sýna að fálkar
geta sótt í hræ langtímum saman,
bæði fullorðnir fuglar og ungir. Eg er
sammála Per Tommeraas um að
hræát sé útbreiddur siður rneðal
fálka. Fálkinn tilheyrir ættkvíslinni
Falco ásamt 36 öðrum tegundum. Að
minnsta kosti fjórar aðrar fálkateg-
undir taka stundum hræ (Falco
berigora, F. biarmicus, F. novaeseelandiae
og F. subniger) (del Hoyo o.fl. 1994).
Flestar fálkategundir aftur á móti,
fálkinn þar á meðal, fela mat ef veiði
er góð. Eg hef oft fundið þessi matar-
búr fálkans við hreiðurklettinn á vor-
in og vitað er að þeir nota þessi
forðabúr þegar veiði daprast og þá
hafa hræin stundum legið og beðið
dögum saman. Miðað við þetta þarf
fálkinn ekki að stíga stórt skref í þró-
unarfræðilegum skilningi til að fara í
hræ sem hann finnur á víðavangi.
Aðlögunargildi hræáts er ótvírætt
fyrir fálkann og væntanlega sérstak-
lega mikilvægt þegar fátt er til fanga
á norðurslóðum á vetuma.
SUMMARY
Some observations on carrion
feeding by Gyrfalcons in Iceland
Tommeraas (1989) reviewed the exist-
ing literature on carrion feeding by Gyr-
falcons Falco rusticolus. He concluded
that carrion feeding was a widespread
phenomenon and involved both adult
and juvenile falcons. This paper gives
some examples of this behaviour from
Iceland. The author has once in winter
seen a Gyrfalcon eat a Ptarmigan Lagop-
us mutus killed some days previously
by flying into overhead wires. Many
more cases are known of Gyrfalcon
coming regularly to baits set out by
hunters to attract Raven Corvus corax or
Arctic Fox Alopex lagopus, or to baits set
out deliberately to feed Gyrfalcons.
At one site in southwest Iceland, a
poultry farm, Gyrfalcons came every
winter for approximately 20 years (ear-
ly 1970s to 1996). The farmer laid out
one hen Gallus domesticus every day
when the falcons were around. They
arrived in November/December and
left in March/April. Up to four or five
birds maximum were seen at the site to-
gether. Only one falcon at a time was
seen to feed on a carcass. The falcons
were seen fighting among themselves
and also driving Ravens away from the
site. The author once visited this site in
winter and observed two falcons, one
juvenile and one adult, perched close by
the remains of a chicken.
At another place in north Iceland,
two Gyrfalcons, an adult and a juvenile,
appeared in the winter of 1990 to 1991
at a site where Ravens had been fed.
The adult falcon soon drove the juve-
nile away and stayed all winter. An
adult falcon, presumably the same bird,
has since over-wintered at this site
(Fig.l). The bird arrives in October and
stays until April. The bird comes to the
house and then sits and waits for the
bait to be laid out. The food, i.e. chunks
of horse meat, calf liver, etc., is not eat-
en on the spot but carried away and ea-
ten somewhere outside the village.
When fed many pieces of meat the fal-
con carries everything away even if it
takes several trips to complete. The fal-
con comes to the house most days if the
3. mynd. Fálkinn Friðrik, Skagaströnd, 3.
mars 1999. - Adult female Gyrfalcon.
Ljósm./Photo: Jóhann Óli Hilmarsson.
weather is bad but less frequently when
the weather is fair and stays away for
days after being fed large quantities of
meat.
I concur with Tommeraas (1989) that
the adaptive significance of this type of
behaviour, carrion feeding, is obvious
and relates to the harsh conditions Gyr-
falcons must cope with. My observa-
tions are all from the winter period and
I would expect that it is during this sea-
son that carrion feeding is most import-
ant for the species. The Gyrfalcon like
other members of the genus Falco cache
prey for later consumption. This behav-
iour can be viewed as a pre-adaptation
to carrion feeding.
I’AKKIR
Arnþór Garðarsson las greinina yfir í handriti og kom með góðar ábend-
ingar.
Heimildir
Cramp, S. & K.E.L. Simmons 1980. The Birds of the Western Palearctic. 2.
bindi. Oxford University Press, Oxford, London, New York.
Hallgrímur Vigfússon 1938. Fálki gerist hræfugl. Náttúrufræðingurinn 8.
128.
del Hoyo, ]., A. Elliott & J. Sargatal (ritstj.) 1994. Handbook of the birds of
the world. Lynx Ediciones, Barcelona.
Ólafur K. Nielsen 1999. Gyrfalcon predation on ptarmigan: numerical and
functional responses. Journal of Animal Ecology 68.1034-1050.
Timmermann, G. 1949. Die Vögel Islands. Vísindafélag íslendinga 28.
239-524.
Tommeraas, P.J. 1989. Carrion feeding in the Gyrfalcon Falco rusticolus: a
review. Fauna Norvegica, Seria C, Cinclus, 12. 65-77.
PÓSTFANG HÖFUNDAR / ÁUTHORS'S ADDRESS
Ólafur K. Nielsen
Náttúrufræðistofnun íslands/
Icelandic Institute of Natural History
Pósthólf/Box 5320
IS-125 Reykjavík
okn@ni.is
Um höfundinn
Ólafur K. Nielsen (f. 1954) lauk B.S.-prófi í líffræði frá
Háskóla íslands 1978 og Ph.D.-prófi í vistfræði frá
Cornell-háskóla í Bandaríkjunum 1986. Ólafur starfaði
hjá Líffræðistofnun Háskólans 1986-1993 og starfar nú
hjá Náttúrufræðistofnun íslands.
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