Sterna, bind 13 nr 1 (PDF-fil) - Museum Stavanger

SUMMARY: OBSERVATIONS OF SOME NESTING BIRDS
AT ØSTENSJØVANNET IN OSLO 1973
The Grcat Crcsted Grebe (Podiceps erislalus) dcfinitely nested for the first time
in 1972. In 1973 at leat two pairs nestcd.
A pair of Mutc Swans (Cygrius olor) rearcd 6 young.
The Coots (Firlica arra) started egg-laying at the end of April and beginning of
May. Fig. I shows the location of 33 nests at the edge of the lake. Since the water
fell iifter ncsting began the edge of one ncst lay as much as 72 cm above the water
Icvel.
The Black-headcd Gull (Larus ridiburidus). Table 1 and Fig. 2 show the total
ncsting population (about 1.800 pairs) and its distribution in the arca. Considerablc
movernents took place in the colony. This was due, amongst other things, to the
establishrncnt of 2 islanils (F 1 and F 2) in the southern half of the lake. Egg-laying
started this year 14 days after the icc had melted from the lakc.
Author's nildress: Zoological Laboratory, University of Oslo,
Bliiitlern, Oslo 3, Nonvay.