The effects of hand-rearing on wild gamebird populations.

Abstract

There can be no doubt that many hand-reared gamebirds have lower rates of survival and breeding success than their wild counterparts. Although releasing birds is an efficient method of increasing autumn populations this may result in the productivity of subsequent breeding populations being depressed. The extent of this depression appears small for grey partridge, moderate for pheasant and large for chukar (or hybrids with red-legged partridge) released into areas with wild red-legged partridges. With the exception of the latter case, rearing does not appear to be an important cause for the observed declines in many bird species. The possible causes of the poor performance of the released birds are discussed. There is evidence to support all three arguments, lack of parental influence, parasitism and genetic effects. The actual causes are likely to vary between different populations and to be a combination of all three factors.