Náttúrufræðingurinn - 1995, Side 46

and breeding distribution of the North At-
lantic gannet Sula bassana and an assess-
ment of the changes which have occurred
since Operation Seafarer 1969/70. Nature
Conservancy Council. Research and survey
in nature conservation. No. 4.
Þorsteinn Einarsson 1954. Talning súlunnar í
Eldey. Náttúrufræðingurinn 24. 158-160.
Þorsteinn Einarsson 1973. Súlubyggðin í
Máfadrang við Dyrhólaey. Týli 3. 71-72.
Þorsteinn Einarsson 1987. íslenskar súlu-
byggðir og saga þeirra. Náttúrufræðingurinn
57. 163-184.
SUMMARY
NuMBERS OF GANNET (SuLA BASSANAj IN
lCELAND 1989-94
Icelandic gannet colonies form two separate
groups, a southwestern group of Eldey and
four isles in the Vestmannaeyjar, and an east-
em group of three recently established colo-
nies, Raudinupur, Skomvik and Skrudur. Cen-
suses of all gannet colonies in Iceland were
made in 1989 and 1994, using aerial photogra-
phy. In addition the three East Coast coloriies
were covered in 1992 and Skmdur in 1987.
Colonies were photographed at altitudes of
100-300 m using a handheld 6x6 cm camera,
with a 250 mm lens and positive colour film.
Three colonies on tops of islands, Eldey,
Sulnasker and Geldungur, were photographed
vertically at altitudes of 200-600 m using a 80
mm lens. Counts were generally made directly
from the film under a dissection microscope,
each site being marked on an acetate overlay
as counted.
The total number in the southwestem group
(Table 1) remained at about 22000 sites in
1983-89 but increased to about 23000 in 1994.
Repeated observations and photography
showed that non-breeders on top of Stori-
Geldungur in Vestmannaeyjar had been
counted as breeders in 1983 and 1985. In this
paper the fígures have been revised, resulting
in totals for Geldungasker corrected to 1440 in
1983 (instead of 1594) and 1319 in 1985 (in-
stead of 2249). At Sulnasker numbers in-
creased from 3600 sites in 1983-85 to 4400 in
1994, corresponding to an annual increase of
about 2%. This is the only significant change
in numbers in the Vestmannaeyjar in 1983 to
1994, as no change occurred at Brandur,
Hellisey or Geldungur. Numbers in Eldey
were almost the same in 1994 as in 1983, al-
though somewhat lower in 1985-89.
Numbers in the eastem group increased
from 1550 sites in 1984 to 2300 in 1994, corre-
sponding to an annual rate of increase of 4.2%
(Table 2), slightly less than the 6.8% up to
1984. The rate was similar in all the colonies,
4.0% at Raudinupur, 3.5% at Skoruvik and
4.4% at Skrudur. The increase at Raudinupur
was mainly on the stack Karl, and at Skoruvik
mainly on ledges in the cliff. The two separate
cliff colonies at Skmdur had begun to merge in
1994.
Counts and surveys of Icelandic gannet
colonies after 1980,have always covered all
colonies. Statements'(Wanless 1987, Lloyd et
al. 1991) that a colony, Máfadrangur at
Dyrhólaey was not included, are mistaken. Al-
though gannets were reported as nesting on
Máfadrangur in 1962 (Einarsson 1973), they
have not nested there recently and only non-
breeders have been recorded there in frequent
surveys from 1974 on (Gardarsson 1989).
PÓSTFANG HÖFUNDAR
Arnþór Garðarsson
Líffræðistofnun háskólans
Grensásvegi 12
108 REYKJAVÍK
Author's ADDRESS
Amthor Gardarsson,
Department of Biology,
University of Iceland,
Grensasvegur 12,
IS-108 Reykjavik, Iceland.
208