Individual and Environmental Determinants of Daily Black Grouse Nest Survival Rates at Variable Predator Densities

Abstract

Nest predation in ground nesting black grouse (Tetrao tetrix) inhabiting managed boreal forests is arguably the single most important cause of nesting failure. Little is known, however, about indirect effects of other factors, such as maternal or environmental properties, and to what extent maternal and habitat qualities interact with varying levels of predator densities. Using an information-theoretical approach, we studied maternal and environmental determinants of daily nest survival rates under variable predator densities of 210 individual black grouse hens in central Finland. Environmental determinants were far more important than maternal ones, and the effects were more apparent at higher predator densities. Keeping predator densities constant, daily nest survival rates increased with nest conspicuousness and increasing tree density, and were higher in undrained areas. While there was no difference between adults and juveniles, hens that invested more in egg size were more successful. Therefore, env...