The importance of protected areas as nocturnal feeding grounds for dabbling ducks wintering in western France

Abstract

We studied the diurnal and nocturnal habitat use of wintering dabbling ducks ( Anas spp.) in two protected areas of an internationally important winter quarter in western France. The waterbodies of the reserves are heavily used by ducks during daylight hours, and 3–55% of these birds used the reserves at night: >50% of shoveler ( A. clypeata), 20% of granivorous ducks (mallard A. platyrhynchos, teal A. crecca and pintail A. acuta), and lower numbers of herbivores (wigeon A. penelope and gadwall A. strepera). Radio-tracking showed that some ducks used the reserves by day and by night, and that some of them may switch from one protected site to another: radio-tagged birds were located in one of the two protected areas for 76% of the days and 81% of the nights they were sought, with granivores switching from waterbodies to wet grasslands within a reserve between the two periods. Such resident individuals may be ‘experienced’ wintering ducks, avoiding surrounding unprotected feeding habitats at night, while birds that leave the reserves at night may be subdominants and/or ‘naı̈ve’ individuals from a transient migratory sub-population. This study suggests that management of nature reserves should combine day-roosts with significant areas of nocturnal feeding grounds, since in protected areas both habitats may be successively used by wintering dabbling ducks across the 24-h cycle.