Ecology of juvenile grouse during the transition to adulthood

Abstract

Abstract Information on survival and habitat use of juvenile animals during the transition period from parental independence to adulthood is sparse, yet survival during this period may be critical for maintaining populations. We review studies on habitat use and survival of juvenile grouse from hatch to recruitment to breeding populations the next spring. Mortality of juveniles was highest during the first 2 weeks after hatch, caused primarily by predation and exposure. Survival of juveniles during their first autumn and winter was usually lower than adults, particularly in autumn. Predation, mainly by raptors, was the main mortality agent. Juveniles did not appear to be more susceptible than adults to hunting, although hunting mortality was additive to overwinter mortality for several species or populations. For most species, juvenile survival was not related to movement distances or patterns. However, studies on grouse in forest habitats disconnected by extensive logging showed that dispersal distances increased and survival was reduced. During the first few weeks of life, chicks eat primarily insects and brood hens seek habitats that optimize a trade‐off between insect abundance and cover. Vegetation must provide sufficient cover to impede predation but be sparse enough to allow movement of chicks. For most species, juveniles and adults used similar habitats in autumn and winter, although juveniles had higher variation in habitat use than adults, possibly due to the greater distances moved by juveniles during dispersal. Habitat use varied more between genders than age classes. Management actions should be directed towards the two demographic bottlenecks for juvenile survival: the first 2 weeks after hatch and the period of autumn when independent young are dispersing. The most direct management actions are the retention or restoration of brood‐rearing habitats, the reduction of habitat fragmentation and the reduction of hunting during autumn movements and in source populations.