Náttúrufræðingurinn - 1992, Side 73

(June-July) and one from winter (De-
cember) (Fig. 6). Geographical distri-
bution of the records is shown in Fig.
7. Ten specimens in the IMNH, col-
lected during autumn, include two
adult males and eight immatures (six
females and two males). Four speci-
mens from spring are immatures (two
males and two females). These va-
grants probably originate from North-
and West-Europe, as indicated by
three recoveries of Kestrels banded as
nestlings (one from the Netherlands
and two from Sweden).
12. Red-footed Falcon (Falco vespertin-
us). Three records: adult male July
1980, adult male April 1981, and male
April 1985.
13. Hobby (Falco subbuteo). Seven rec-
ords, all from spring (three, April)
and summer (four, June-July).
14. Peregrine Falcon (Falco peregrinus).
Four records: adult male July 1961,
immature female October 1985, one
October 1986, and immature female
December 1988. The first two birds
belong to the nearctic race F.p. tun-
drius.
Most of these raptors strayed to Iceland
during the migration period of the species
in question. Raptors can be divided into
two groups according to their mode of
travel during migration (Newton 1979).
The first group “soarers” is represented
by relatively large raptors with long broad
and rounded wings, e.g. eagles, buzzards
and vultures. These birds depend heavily
on thermal updrafts on their journeys,
tliey travel mostly over land, and if they
have to cross oceans they use the shortest
possible route, e.g. narrow straits. The
second group “flappers” is composed of
small to medium size raptors with long
and narrow wings. These birds are not de-
pendent on thermal updrafts and travel
readily over open water. The accipiters
form an intermediate group, they regular-
ly use thermal updrafts but also travel
readily over open water. “Flappers” are
more common as vagrants in Iceland (9
species, 92 records) than “soarers” (5 spe-
cies, 18 records). This probably reflects
the reluctance of “soarers” to travel over
open water. The ratio of these two
groups, “soarers” versus “flappers”, is
more equal in the avifaunas where Ice-
landic raptors originate, Europe and
North-America.
Before 1940 only two of these 14 species
had been recorded in Iceland (Kestrel one
record, Osprey two records). Since 1940
there has been a drastic increase (Fig. 8).
This increase is believed to be caused
primarily by increased number of observ-
ers.
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