Fróðskaparrit - 01.01.1983, Síða 83

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THE AUTUMN MIGRATION AT AKRABERG,...
It was obvious that the condition of the re-
maining birds, individuals of Robins especi-
ally, became worse and worse.
The Sylviae, Blackcap especially, had
another pattern of arrival (appendix 2), as the
number was gradually increasing to a cul-
mination on Sep. 28th and after that new
arrivals on Oct. 3rd and 7th.
The migration of Continental smaller birds
was completely dominated by species migrat-
ing by night. Even common species, migrating
by day, such as Skylark, Brambling Fringilla
montifringilla, and Chaffinch Fringilla coelebs,
were only seen in very small numbers
(appendix 2).
The origin of the birds. The first large wave
of »night migrants« unđoubtedly came from
Northern Scandinavia, considering the dis-
persion of species and the Scandinavian wind
conditions. The period from Sep. 24th to Oct.
3rd. also brought birds of a southeasterly
origin (Barred Warbler Sylvia nisoria, Red-
backed Shrike Lanius collurio, Red-breasted
Flycatcher Ficedula parva, Scarlet Rosefinch
Carpodacus erythrinus). These occurrences
coincide with fair southeasterly winds all the
way from the Baltic area, i.e. favourable winds
for birds migrating reversely. Also the Black-
caps from the same days are best interpreted
as a consequence of reverse migration from
the SE or the E.
Far eastern species were represented by
Yellow-browed Warbler on Sep. 20th and
27 th, and moreover, the period between Oct.
9th and 1 lth, when the wind was northeaster-
ly from northern Finland, resulted in Red-
throated Pipit, Little Bunting, and Chiffchaffs
with abietinus/tristis-characters. Unfortuna-
tely the observations stopped on Oct. llth,
the same day as the Fair Isle had unusually
many Pallas’s Warblers Phylloscopus prore-
gulus, among others (FIBO Report 1982).
Discussion.
Residents. Some of the birds, which have been
considered as residents up to now, were seen
migrating or intending to migrate (appendix
1): House Sparrow Passer domesticus, Rock
Pipit, and Raven Corvus corax. In the case of
Rock Pipit, straying immatures do not ex-
plain the extent of migration. On the Fair
Isle movement of the Rock Pipit has also been
observed recently (FIBO Report 1982).
The conditions of the isolated islands in
the North Atlantic have established some
resident populations, often resulting in local
subspecies. This tendency must not be over-
estimated and the observations indicate that
the enforced passage of a seadistance of at
least 300 km is of less importance than
assumed by Salomonsen (1935, 1963).
Local migrants. Most Faroese migrants are
migrating by day, but only a few were ob-
served during the period of observation (ap-
pendix 1). Compared to previous observa-
tions (Potts 1961), this indicates that a large
part of the local migration has finisheđ before
the middle of September. The observations
during the present period contain more in-
formation about the final performance of
migration, which, as far as for instance
Whimbrel Numenius phaeopus is concerned,
turned out to last even to the middle of Octo-
ber. However, concerning the studies of local
migration, it is a great problem that, without
ringing, the Faroese populations cannot be
distinguished from corresponding Icelandic