The breeding ecology of the Mute Swan Cygnus olor in Poland - preliminary report

Abstract

Data were collected in three places in Poland: Gdansk area, the reserve "Przemkow Ponds” and the Milicz fish ponds. The Mute Swans from northern Poland (Gdansk area) nested later than those in Silesia which is located in south-western part of country. The difference in the occurrence of the peak of first egg laying was about 20 days though after mild winters it was smaller ( aprox. 10 days). The mean clutch size was very similar in all three areas and it varied between 5.8 and 6.2. However, swans from the Gdansk area laid larger eggs than those from Silesia. Mean number of fledged cygnets per succesful pair (which raised at least one cygnet) varied betwen 4.1 and 4.3. The production of young per breeding pair was estimated at 2.8-3.3. Pairs which started to breed before 20 April had larger clutches, laid bigger eggs, and produced more cygnets than those breeding late (after 20 April).