Náttúrufræðingurinn - 1980, Side 177

never nesting in stone walls like nowadays.
During same period, Wheatears were
common. Snow Buntings have increased in
numbers since 1965. The numbers nesting
on Flatey is among the densest known for
Iceland. Few pairs nest in the other islets.
Summarizing remarks
A faunistic report, as complete as that in
the present paper, has not been published
for other islands around the coasts of Ice-
land, with the possible exception of Grímsey.
Much information is still unpublished on
the subject, for other Breidafjördur islands
including.
Since the start of my investigations in
1974, 26 species have been recorded nesting
in the area. Three more are known to have
nested prior to that, a total of 29 species.
Twenty-six of these have been recorded from
Flatey itself, including the three which have
not been found after 1974. Altogether 19
species have been found nesting in all the
islets south of Flatey.
Remarks on selected species
Redshank and Snipe
These are the most common wader species
on Flatey itself, with an average density of
ab. 90 prs/km2 (Snipe), and ab. 80 prs/km2
(Redshank). This is unusually dense com-
parcd to other areas in Iceland (e.g. Glue
1970). Nielsen (1979) recorded 9 and 26
prs/km2 (Redshank), and 21 and 30 prs/km2
(Snipe) in the vicinity of the food-rich area
of Myvatn (NE. Iceland).
The difference between Flatey, on one
hand, and the adjoining islets on the other, is
quite striking. I believe this is the result of:
(a) Flatey being inhabited, and (b) Unequal
predation by Ravens. Ravens frequent thc
islands in the search for eggs, during the
time when most birds are laying. Since
Ravens are constantly sought to kill,
they are relatively more common outside the
immediate vicinity of the inhabited part of
Flatey. In 1975 eggs disappeared from Snipe
and Redshank nests unusually much on thc
eastern part of Flatey compared to the
western part. The difference was statistically
significant (Redshank: Xf =20.14,
P <0.001; Snipe:Xi = 6.0, P < 0.05).
Snipe are rare breeders in the is-
lets south of F'latey, and nest on Flatey
most densely on the western half. Redshank
are more common than Snipe in the islets,
and nest density on Flatey is greatest on the
eastern half. Redshank nests are normally
much better concealed than those of Snipe,
and therefore presumably less vulnerable to
Raven predation. The present-day breeding
distribution of these species may thcrefore
be explained by an unequal predation, not
necessarily resulting in changes in numbers
of breeding birds.
Black Guillemots, and possible influence of
Mink and Brown Rats
Table II and Fig. 5 show that Black
Guillemots have increased notably in recent
years. This has also taken place in other is-
lands belonging to Flatey, and probably
over the whole of Flatey civil parish (A.
Petersen, unpubl.).
Rats probably kept Black Guillemots
away from Flatey 1940 onwards. Rats
are known to have effects on seabird
populations (Joensen 1966, Parslow 1973,
Crantp, Bourne & Saunders 1974, Atkinson
1978, Imber 1978).
Rats first colonized Flatey in the early
years of the 19th century, but were
exterminated 7 years later (Sívertsen 1840).
Flatey was again colonized by rats in 1896,
and they became very troublesome by
spoiling fish hung for drying in open sheds.
(S. Gunnlaugsson, pers. comm.). Hörring
also remarked on this in 1908. In the 1930,’s
rats were very common, but primarily on the
western half of Flatey, in the settlement
area. When people started moving away
from Flatey in the 1940’s, rats begin spread-
ing also to the eastern half, coloniz-
ing some of the islets. Rats were still very
common in 1965, when start was made in
trying to eradicate them. A real effort was
not put into this until in winters 1969/70
and 1970/71, and from February 1971 on-
wards no rats (or mice) have been seen in the
islands.
Contrary to what one would expect from
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