Impact of hunting on the population dynamics of wild birds.

Abstract

The population dynamics of wild birds are the result of two competing processes, gains and losses, which, for European huntable species, correspond broadly to the breeding season and non-breeding season respectively. The relative stability of populations shows that one or (usually) both of these processes are density-dependent, with relationships that depend on the environment. It is thus environmental conditions that determine variation in long-term population size. Hunting increases the losses outside the breeding season, and is often itself density-dependent. The increased losses reduce population size, thereby triggering a density-dependent reduction in non-hunting losses and a density-dependent increase in gains. The compensation for hunting losses that ensues varies from species to species, but it is never perfect. Consequently, all else being equal, the long-term effect of hunting is to reduce population size below what it would be if it were not hunted. For a range of hunting pressures, there is a range of reduced long-term population sizes, each of which is stable and sustainable (even beyond maximum sustainable yield). Beyond this range, hunting becomes unsustainable and leads to extinction. Contrary to appearances so far, hunting is not a purely negative phenomenon because all else needs not be equal. At a given intensity of hunting, long-term population size is determined by environmental conditions via density-dependent gains and losses. Appropriate environmental management by hunters can produce a population whose sustainable size, despite hunting, is much larger than in an unhunted, unmanaged, situation. Such hunter-quarry interaction, where hunting is the incentive for the hunter to manage, and which benefits both hunter and quarry, constitutes Conservation through Wise Use. The principle of Conservation through Wise Use should be applied on Protected Areas in Europe, to the mutual benefit of humans and birds.