Habitat requirements of breeding waterfowl on gravel quarries: management implications.

Abstract

Nest success and duckling survival of mallard and tufted ducks were studied at two sites in North Buckinghamshire in order to aid habitat management. Mallard nest success was highest for island nests and for nests in tall vegetation. Nests of both species were aggregated in patches of tall vegetation although the proportion of nests destroyed by predators increased with an increase in nest density between years. The most critical time for ducklings was shown to be during the first twelve days; ducklings hatched during the peak in the chironomid food supply survived better than those hatching before or after this peak. Consequently, broods spent more time feeding in areas with high food supplies. The river Ouse was used extensively by broods; broods moving long distances in search of food suffered heavier mortality than those moving short distances. The feeding range of females prior to hatching was smaller than the brood ranges. Once a brood died the female often changed her range to incorporate 'loafing' sites. Management should be concerned with providing: i) nest-sites conducive to high nest success i.e. islands with tall vegetation, i i) brood rearing areas in shallow water close to nest sites, i i i) loafing sites providing visibility of potential predators.