The food of Mallard ducklings in a wet gravel quarry, and its relation to duckling survival.

Abstract

The area of flooded gravel quarry habitat is increasing annually and these artificial wetlands could help to replace and, in some cases supplement, natural wetlands, making a significant contribution to the production of indigenous wildfowl species. The W.A.G.B.I. (Wildfowlers' Association of Great Britain and Ireland, forerunner to B.A.S.C., British Association for Shooting and Conservation) - Wildfowl Trust Gravel Pit Reserve at Sevenoaks, Kent is an example of this. There is, however, a major problem with the rapid establishment of breeding wildfowl populations on very recently restored gravel workings, and this is the unduly high mortality among downy ducklings, especially those of the Mallard Anas platyrhynchos. The principal aim of the Game Conservancy's Wildfowl Project is to determine the factors which affect the survival rate of Mallard ducklings so that management plans for new gravel pit reserves can be altered accordingly.

Duckling mortality in the gravel pit study area at Great Linford, Buckinghamshire, has been consistently high, around 77% over the period of the study. This is in a situation where predators, with the exception of Pike Esox lucius, are rigorously controlled and where it can be assumed that predation is not the major cause of duckling losses. This paper presents the results of the analyses of the gut contents of 99 wild Mallard ducklings from 0-45 days old which were collected in the study area over four seasons.

The emergence of insects from the reserve was monitored in 1975 and 1976 by the use of insect emergence traps and by sweep netting. Some of the results of this survey are presented, and the availability of adult insects is related to the survival of Mallard ducklings.