Habitat requirements of breeding waterfowl on inland waters.

Abstract

Britain has lost many natural wetlands and is rapidly losing the remainder because of increased drainage of agricultural land. At the same time there has been an increase in the abundance of man-made wetlands as a consequence of i) increased gravel extraction for use on our expanding motorway system and for the building industry, and i i) the construction of reservoirs. To some extent then, the gravel industry in particular is supplementing the loss of our natural wetlands. These man-made wetlands are obviously immature with little aquatic vegetation and therefore the number and relative abundance of species inhabiting them is far smaller than on more mature wetlands.

Two waterfowl species in particular, the mallard (Anas platyrhynchos) and the tufted duck (Aythya fuligula) have become well adapted to exploiting the resources offered by flooded gravel quarries. However, previous research at Great Linford suggested that breeding success in these two species was low because of high nest predation and high duckling mortality. Little was previously known of the dynamics of nest predation or whether density dependence existed, at in some species (Dunn, 1977; Potts, 1980). Previous knowledge of ducklings was limited to diet (Chura, 1961; Street, 1977), and little work had involved determination of survival or of attributes of the home range (Talent, Krapu & Jarvis, 1982).

This paper aims to a) determine nest success in both species and the factors influencing vulnerability to predation, b) investigate density dependent nest predation in mallard, c) investigate factors influencing duckling surviva1, and d) compare female ranges after brood loss with the brood home range to determine how different resources are partitioned through the breeding season.