Náttúrufræðingurinn - 1956, Page 28

136
NÁTTÚRUFRÆÐIN GURINN
1
does not nest on top of high, rocky islands and stacks. All the major kittiwake
colonies in Icelancl are situated on exposed headlands or outlying islands and
kittiwakes hardly ever nest in the inner parfs of fjords and bays.
On the towering bird cliffs of Iceland, which are occupied by a ntixed ass-
embly of cliff-breeding sea birds, the kittiwake is one of the commonest and
most conspicuous species. Here it mainly occupies the lower and middle parts
of the cliffs and it also frequently nests well inside surf-eroded caves at the foot
of the cliffs. Some nests may even be located so low that they are exposed to the
spray of the sea, which may prove fatal in some cases. The nest is usually built
on small projections or footholds on the cliff face or on small, narrow ledges. >
The kittiwake therefore does not seriously compete with other species for nest-
sites although there is a considerable overlapping in the nest-site perference
of the kittiwake and the common and Briinnich’s guillemots, especially the
latter. The nest is built of grasses, mosses and seaweeds, with tangles of nest
material often dangling down from the outer edge of the nest. The nest material
is cemented together and the wliole nest structure securely plastered on to the
rock by wet seaweeds, mud and excrement. If the nests are not swept away
during the winter they are used year after year, frcsh material being added
each year on top of the old nest, which may thus gradually become quite bulky.
The clutch consists of 1—3 eggs, 2 eggs being by far the commonest clutch
size in Iceland.
In August, when the young become fledged, the kittivakes gradually desert
the breeding colonies and now they spread round all the coasts, also pene-
trating in to thc inner parts of bays and fjords. A lieavy mortality among the
young often occurs at this time of the year and their carcasses are often found
washed upon the shore in large numbers. Tlie seaward movement of kitti-
wakes begins as early as August and by the end of September most have
left inshore waters. Single birds or small ílocks may liowever remain in the
vicinity of the coast, even in fjords and ports, throughout the winter. In-
shore movement on a large scale begins in March and conlinues throughout
April and May. On the south coast, cspecially in the Westmann Islands,
kittiwakes are, however, said to begin to arrive much earlier, even at the
end of January. Birds begin to visit breeding stations as early as Marcli,
but these are not occupied before the middle of April. Nest building begins
early, or in the last thircl of this montli, altliough the eggs are not laid be-
fore late May or early June. In tlie Westmann Islands, it is true, sorne birds
are said to lay considerably earlier.
In early spring kittiwakes sometimes visit fresh-water near tlie shore and
in the breeding-season they regularly gather on fresh-water lochs in the
vicinity of the nesting cliffs. During this period large flocks of kittiwakes |
may also rest on tlie shore or at sonte distance inland around the nesting
cliffs. Furthermore kittiwakes collecting nest material regularly fly inland,
and 1 have encountered such collecting parties at a distance of 8 km from
tlie shore. With the exception of solitary stragglers kittiwakes are not met
with inland at otlier times of the year.
Kittiwakes ringed as adults in Iceland liave been recovered in the Faroe