Náttúrufræðingurinn - 1952, Blaðsíða 33

ÍSLENZKIR FUGLAR
77
Foreldrarnir skiptast A um að liggja á eggjunum og hjálpast að við að annast ungana
og að afla þeim fæðu. Hlutur kvenfuglsins í útúnguninni er þó mun mciri cn karl-
fuglsins. Hér á landi fer lómurinn að vitja varpstöðvanna í maí, og varptíminn er
seint í mai eða snemma í júní. Fer það nokkuð eftir veðurfari og hvenær isa leysir af
vötnum.
Islenzkir lómar eru að miklu leyti farfuglar. Leita þeir a haustin til Bretlandseyja
og meginlandsstranda Vestur-Evrópu, en í apríl eða snemma í maí koma þeir aftur.
DálítiII slæðingur af lóin heldur sig þó við Suðvesturland allan veturinn, á sömu slóð-
um og himbriminn, en óvfst er, hvort hér er um íslenzka fugla að ræða eða fugla frá
norðlægari íshafslöndum. Á vetrum heldur lómurinn sig yfirleitt á sjó, með ströndum
fram, sjaldan á ósöltu vatni.
Eins og himbriminn lifir lómurinn mikið á silungi, en einnig á ýmsum sjávarfiskum
(t. d. sandsíli), og ennfremur á krabbadýrum og lindýrum.
SUMMARY
Icelandic birds II. The Red-Throatf.d Diver (Colymbus stcllatus Pontopp.)
The red-throated diver is a fairly common and widely distributed breeding bird in
Iceland. Unlike the great northern diver it is mainly confined to he lowlands and
valleys where it occupies the smaller lakes and tarns and very occasionally calm rivers
or river mouths. But it is, nevertheless, known to breed in a few places in the Central
Highlands, for instance in Thjórsárver at Hofsjökull right in the centre of Iceland 500—
600 meters above sea level. The red-throated diver prefers lakes or tarns with some
marginal vegetation, even it these may contain no fisk. In such cases the birds often
have to fly considerahle distances for their food, either to the sea or the the nearest
lakes containing fish. As a rule the red-throated divcr breeds singly in Iceland or only
one pair on each lake or tarn. But in a few places (Krossvatn in Skardströnd, Breida-
merkursandur) several pairs (up to 20) may breed together thus forming small colonies.
On the whole it may bc said that the red-throated and the great northern divers ex-
cludc each other as they never seent to breed on the same lake.
The nest of the red-throated diver is very similar to tliat of the great northern diver,
but smaller (diameter 27—28 cm, depth 4—5,5 cm) and often lined with somewhat
bigger quantities of wet moss or other vegetable matter. It is alway near to the edge of
the water, and the worn pathway leading from the nest to water is usually very con-
spicuous. The clutch consists of two eggs, very occasionally of only one egg.
In Iceland the red-throatcd diver is probahly mainly migratory. It is true that in
winter single birds are not rarely met with along the coasts of the sotith-western parts
of Iceland. But these hirds may well be of arctic (Greenland) origin. The bulk of the
Icelandic red-throated diver population is supposed (no recoveries of marked birds are
available) to spend the winter along the coasts of the British Isles and Continental
Western Europe. In spring the red-throated diver arrives in Iceland in April or in
early May. On its arrival it frequents the fjords and estuaries, returning to the breeding
lakes as soon as they bccome icefree. In late May, or more commonly in early June, the
eggs are laid, and the birds stay on fresh water until the young ones are fledged. Trout
and char constitute an important part of the food of the red-throated diver in Iceland,
both in fresh water and in the sea, but detailed investigations of it’s diet have not been
carried out.