Habitat quality and gamebird population ecology.
An animal's habitat may be defined as the set of environmental characteristics or resources upon which it depends for its survival. These include the food supplies of both adults and young, a suitable site for breeding, and some form of protection against predators and inclement weather. Variation in the quantity of these specific resources determines the quality of the habitat.
To understand how resource variation affects the population size of any animal, it is necessary to examine the relationships between habitat quality and the processes which alter survival and reproductive output of individuals within that population. The objective of this chapter is to illustrate how habitat quality can influence population processes in gamebirds, and then to show how an understanding of these interactions can be used in the management of gamebird populations.
I have chosen to concentrate on the two most intensively studied gamebird species in Britain, namely the red grouse and the grey partridge (which represent upland and lowland gamebirds respectively). The approach adopted in the study of each species has been quite different. The early observation that red grouse populations showed large fluctuations in numbers (Lovat, 1911) eventually led to investigations of the behavioural and other mechanisms which limit populations and can cause changes in numbers (see Moss and Watson, 1985; Hudson, 1986a). By contrast, the study of the grey partridge stemmed from the concern over its decline as a major quarry species; this prompted a long-term investigation of the effects of modern agriculture, predation and game management on the species' population ecology (see Potts, 1986). Thus ecological studies of the red grouse were designed to answer theoretical questions relating to population regulation, whereas our knowledge of the ecology of the grey partridge has its origins in the practical problem of how to halt the species' decline.
Ultimately, the information collected on both species can be used as a basis upon which management practices can be built for the conservation of game. The examples discussed below will not only demonstrate this, but will also show that a scientific basis for the management of animal populations has much to offer the wider field of wildlife conservation.