Feeding activities of Bewick's Swans Cygnus columbianus bewickii at a migratory site in the Estonian SSR

Abstract

Observations were made of up to 928 Bewick’s and 63 Whooper Swans staging at Matsalu Bay, Estonia over a 10 day period from 24 April to 3 May 1988. Bewick’s Swans out-numbered the Whooper Swans by a ratio of 33 : 1 during the study period, which differed from the 3 : 1 Bewick’s to Whooper Swan ratio reported in the immediately preceding years. The maximum count of 1,800 migratory swans recorded on the Matsalu State Nature Reserve in spring 1988 was also low, however, and the missing birds were thought to be mainly Whooper Swans. Flock scans of swans visible from Haeska, on the north shore of Matsalu Bay, found that on average 59.0% of birds were feeding and 24.5% were sleeping, reinforcing the view that the site is important to the birds for resting and replenishing their nutrient reserves during spring migration. The data were compared with observations made of Bewick’s Swans wintering in Gloucestershire, and also with the activities of birds grazing in fields in Estonia. There was no sexual difference in the feeding rates recorded for paired males and females at Matsalu Bay, although paired birds looked up for shorter periods whilst feeding than did single swans and cygnets. Bewick’s Swans were observed mating in Estonia in spring 1987. Cygnets continued to associate with their parents during the spring migration.