Factors affecting chick mortality of hazel grouse in a temperate forest, South Korea

•Factors affecting chick mortality of hazel grouse was studied in a temperate forest.•Mortality of chicks is lower in dense understory cover and natural deciduous forest.•Moreover, distance from forest road and overstory cover were important variables.•Understory cover and natural deciduous forest should be maintained for the species. Between March 2006 and September 2013, hazel grouse Bonasa bonasia (35 hens and 157 chicks) were equipped with radio transmitters in a temperate forest, South Korea to document factors influencing chick mortality. We recorded habitat composition, mortality rates, and cause of death. Among 157 hazel grouse chicks, 75 survived and 58 were killed by predators. The mean spring–summer survival of chicks was 48% and mortality due to predation was 37%. According to the habitat composition analysis, natural deciduous forest was used by hazel grouse chicks significantly more often than the other forest types. The top-ranked model (r2=0.76) for hazel grouse chick mortality included understory cover, forest type, distance from the nearest forest road, and overstory cover as the dominant variables for the mortality of hazel grouse chicks. This model had an Akaike weight of 0.72, which suggests strong model certainty. This study suggests that forest managers who want to protect of hazel grouse should aim for denser understory cover and higher portions of natural deciduous forest.