Náttúrufræðingurinn - 1952, Blaðsíða 53

ÍSLENZKIR FUGLAR
45
ágúst og í september fer himbriminn að leita til sjávar aftur, og á veturna heldur hann
sig með ströndum fram, oft alveg uppi í landsteinum.
Sumt af íslenzka himbrimanum fer af landi burt á haustin (í sept.) og hefur vetrar-
dvöl við Bretlandseyjar og meginlandsstrendur Vestur-Evrópu. En nokkur hluti hans
dvelst þó vetrarlangt hér við land, aðallega á svæðinu frá Vestmannaeyjum til Snæfells-
ness. Við norður- og austurland sjást himbrimar ekki á veturna. Hugsanlegt er þó, að
eitthvað af vetrarhimbrimanum við suðvesturland sé aðkomufugl frá Grænlandi. Him-
brimar, er yfirgefa landið á veturna, koma aftur seint í apríl eða snemma í maí.
Himbriminn lifir mjög mikið á silungi, einkurn meðan hann dvelst á ósöltu vatni, en
á veturna lifir hann auk þess á ýmsum sjávarfiskum og líka eitthvað á krabbadýrum og
lindýrum.
SUMMARY
Icei.andic birds I. The Great Nortiiern Diver (Colymbus imrner Briinn.)
In Icelaiul the great northern diver is not an uncommon but scattered breeding
bird throughout the country. In the breeding-season it frequents fresh-water lakes,
especially tlie larger and deeper lakes, rich in trout (Salmo trutta) or char (Salvelinus
alpinus), which constitute its main summer food. But where there is a concentration of
lakes it may also be found breeding on smaller lakes in the vicinity of larger lakes
abounding in fish. It is found breeding both in the lowlands and the highlands, where
its upper limit of distribution lies about 600 m above sea level. It avoides lakes with
rich vegetation and rich and varied bird life. Instead it prefers the solitude of isolated
mountain lakes without marginal vegetation or cover. This habitat it shares with the
whooper swan (Cygnus cygnus) and often also with the long-tailed duck (Clangula hye-
malis), and up to a certain height also with the scaup-dauck (Aythya marila). Owing to
tliese habitat preferences it is more common in the highlands than in the lowlands.
But nevertheless it is known to breed or to have bred on lowland lakes in many parts
of the country, and in a few cases even on lagoon lakes.
In spring the great northern divers return to their breeding lakes as soon as these
become icefree. This usually occurs in May, and in late May or in early June the eggs
are laid. The clutch consists of two eggs, exceptionally only of one egg. As a rule only
one pair occupies each lake in the breeding-season. The nest is either on banks of lakes
or on tiny islands. It is invariably so close to the water that the sitting bird can slide
directly from the nest into the water, a distinct pathway worn by the birds often
leading from the nest to the water. The nest is a large but shallow circular de-
pression in the marshy ground (diameter 37—47 cm and depth 4—10 cm), mostly
lined with some mosses, sedges or other vegetable matter, which the birds collect in
tlie immediate surroundings of the nest. The nest hollow and the nest material is
commonly, but not always, wet. In late August and in September the birds leave the
lakes and return to the sea. During winter great northern divers are frequently ob-
served along the shores of the climatically favourable soutwestern parts of Iceland,
especially in the area from Vestmannaeyjar to Snæfellsnes. On the otber hand they are
never observed in the North and East during winter. But in my opinion there can,
nevertheless, be no doubt that a considerable part of the Icelandic population of this
species Icaves the country in winter and prestimably (no recoveries of ringed birds
are available) spends the wintcr along the shores of the British Isles and perhaps also
along those of continental Western Europe.