Náttúrufræðingurinn - 1970, Síða 51

NÁTTÚRUFRÆÐIN GURINN
45
as many nests as possible by placing tlie eggs in water. Determination of clutch-
size was basetl on only those nests which contained eggs in advanced stages of
incubation (eggs standing up vertically in the water or floating).
The following 28 species were found breeding in the area (see Table 1 for
estimated numbers of breeding pairs and clutch-size of ducks and geese):
Red-throated diver (Gavia slellata). One nest found in 1966 and also
in 1967. No signs of breeding in other years, but connnonly seen.
Slavonian grebe (Pocliceps auritus). One nest found in 1966. Three
birds were seen in 1967, but no signs of breeding. Not seen in other years.
Whooper swan (Cygnus cygnus). Frequently observed, but only one breed-
ing record, in 1965.
Grey-lag goose (Anser anser). Except lor the black-headecl gull the commo-
nest breeding bird. Altogether 273 nests were found, predominantly in the
dwarf shrub ol tlie middle and northern sections. Low-lying nests were
occasionally flooded.
Mallard (Anas platyrhynchos). Moderately common, altogether 34 nests were
found.
Wigeon (Anas penelope). The commonest breeding duck in the area. A
total of 114 nests were found.
Pintail (Anas acuta). None observed in 1964, but one male was seen tlie
following year. In 1966, however, 11 nests were found and 29 in 1967. This
high density seemed to bc maintained at least in 1968. No explanation can
be offered for this dramalic increase. The pintail appears to be an earlier
nester than other ducks with the exception of the eider duck.
Teal (Anas crecca). Moderately common, altogether 22 nests were found.
Shoveler (Anas clypeata). None observed in 1964 and 1965. At least 3 birds
were seen in 1966, and probably 4 the following year. In 1968 one male was
seen and an incubating female discovercd.
Scaup (Aythya marila). A comrnon breeding bird and altogether 47 certain
nests of this species were found, but in many cases positive identification of
Aylhya nests was not possible. Togetlter with other cliving ducks (except the
eider duck) the scaup is a later nester than Anas ducks.
Tufted duck (Aylhya fuligula). A common breeding bird. Altogether 41
positively identified nests were discovered.
Long-tailetl duck (Clangula hyemalis). Rather uncommon, only 7 nests
were found.
Common scoter (Melanitta nigra). Approximately 15 pairs were breeding
in the area in 1964, 1965, and 1966, but in 1967 the population had dropped
to perhaps 4 pairs, and in 1968 not a single bird was seen, although one
probable scoter nest was found containing 2 cold eggs. In 1969 one nest was
found containing 8 eggs. A total of only 6 nests were found in thc area.
■ t seems possible that the Torrey Canyon disaster in England in March 1967
may have been the cause of the observed decline as Icelandic scoters winter
in or near the disaster area.
Red-breasted merganser (Mergus serrator). An uncommom breeding
bird. Only 3 nests were found.