THE BEHAVIOR OF A WINTERING FLOCK OF WHOOPER SWANS CYGNUS-CYGNUS AT ROSTELLAN LAKE, CORK

The behaviour of whooper swans Cygnus cygnus at Rostellan Lake, Cork, was studied over the winter of 1991-2. Behavioral patterns were assess ed by instantaneous scan sampling and focal sampling. No significant v ariation was found between the activity patterns of adult and first-wi nter swans, and thus the flock was treated as a single unit for subseq uent analysis. Feeding and comfort activities accounted for 40% and 44 % respectively of the total seasonal activity. The other major activit ies were vigilance and swimming. The main feeding strategies were upen ding and head and neck submerged whilst feeding on aquatic vegetation. Grazing on agricultural land was observed only once, and only in Febr uary. The diurnal feeding pattern varied over the study: sometimes the re was a linear increase in the percentage of birds engaged in feeding as the day progressed, while on other occasions a pattern of bimodal peaks was observed.