Migration patterns and sex ratios of diving ducks wintering in Northern Ireland with specific reference to Lough Neagh

Abstract

Several duck species exhibit differential migration, whereby females settle further south than males on the winter grounds after the autumn migration. This is most exaggerated in the diving ducks. In Northern Ireland generally, the migration patterns of Common Pochard Aythya ferina, Tufted Duck A. fuligula, Greater Scaup A. marila, and Common Goldeneye Bucephala clangula are similar to those observed in Great Britain. On Lough Neagh in particular, the sex ratios of wintering flocks of diving ducks were observed between the winters of 1996 and 1999. On average, 79% of Common Pochard, 72% of Tuf ted Duck and 66% of Common Goldeneye wintering on Lough Neagh were male. The possible reasons for differential migration of the sexes include body size dimorphism resulting in different cold temperature tolerances, advantages for males in returning to breeding grounds sooner and intersexual competition excluding the less competitive females to areas further south.