Náttúrufræðingurinn - 1953, Side 54

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NÁTTÚRUFRÆÐINGURINN
it is, in all probability, the commonest of all Icelandic birds. It is a highly social
bird, often breeding by the thousands in vast colonies. Solitary pairs are rarely
found breeding quite by themselves, but in some places there are only a few of
them together. Breeding stations are equally common on the mainland coast and
on islands of varying size and height. Large colonies are often found on low-lying,
grassy islands, although the biggest colonies in this country are to be found on
high, uninhabited islands rising steep from the sea. There the puffins inhabit the
cliffs and the steep turfy slopes as well as the turfy tops of the islands. On the
other hand, the puffin is not known to breed anywhere on low-lying shores of the
mainland. There it is restricted to cliffs or steep mountain slopes facing the sea. But
the mainland cliffs inhabited by the puffin may be extremely variable, ranging from
comparatively low crags to perpendicular cliffs of several hundred metres’ height.
Sometimes the puffin nests in natural crevices or holes in the cliffs or under
loose rocks or boulders at the foot of the cliffs. Yet in most cases it burrows in
turf to excavate the nesting site. When breeding in cliffs it is therefore mainly
found at the upper edge of the cliffs or in patches or strips of turf on the cliff face.
When breeding on low-lying, grassy islands with friable soil the length of the
burrow is usually 1—2 m, averaging a little less than 1.5 m. In most cases the bur-
row is more or less curved, sometimes with abrupt turns. The entrance to the bur-
row is either circular (average diameter ca. 15 cm) or, more often, somewhat wider
than high. Usually the burrow descends at a slight angle, especially near the open-
ing. Generally speaking, however, the length and shape of the burrow varies a great
deal in accordance with the nature of the soil and other conditions in each place.
The inshore movement of the puffin in spring occurs in April, mainly about or
soon after the middle of the month. Towards the end of April or in early May
the birds start visiting the nesting stations now and then. Laying begins about or
just after May 20 and lasts until the first week of June. Only one egg is laid. It is
dull white, marked with faint brownish or lilac spots and blotches, often forming
a cap or zone at the big end. Pure white eggs are rare, although in some cases the
markings are so faint that the soiled egg may seem unmarked at first sight. The egg
shell is rough and without lustre. The nest is placed in an enlarged cavity at
the end of the burrow. It is a loose mass of withered grass, sometimes with a few
feathers, in which rests the egg. The first eggs hatch in the last days of June. The
nestling is fed by both parents with small fish (sand-eels and fry of herring and
Gadidae). In the last third of August the young start leaving the burrows after
having been deserted by the parents for several days. The nesting places
are deserted towards the end of August and the first week of September.
Very soon both adults and juveniles disappear from inshore waters and move out
to sea. There is little definite information on the migration and winter range of
the Icelandic puffins. But perhaps they do not go far. Thus solitary, wrecked puf-
fins are not rarely met with during winter in the Vestmannaeyjar (Westmann Is-
lands) off the south coast. Moreover puffins are known to winter in the waters
north of Iceland. This is manifested by the fact that in winters when the fjords and
bays of the north coast are suddenly filled with polar ice, considerable numbers of
puffins may be found dead or starving on the ice. But it is uncertain whether these
birds are of Icelandic origin. They could just as well be puffins from Jan Mayen,
Spitzbergen or even Northern Norway.