Although nocturnal habitats are often critical to avian survival, they are relatively unstudied. Nocturnal roost habitat selection may be particularly important for Ruffed Grouse (Bonasa umbellus) broods, which experience high mortality due to predation and exposure in the first few weeks after hatching. Because these habitats may have important consequences for Ruffed Grouse productivity and abundance, and little is known about them, we assessed nocturnal roost habitat selection of Ruffed Grouse broods and the influence of habitat features on brood survival in central Pennsylvania. Roost use changed through time, with grouse broods roosting on the ground in the first five weeks after hatching and arboreally thereafter. Broods selected roost sites with greater deciduous canopy cover, coarser woody debris, and more concealing cover than at random sites. Habitat did not differ between ground and arboreal roosts. Brood survival declined from a mean 0.90 in the first week to 0.38 through the fifth week and was negatively affected by increasing stem density. Roost use is likely determined by developmental constraints on the thermoregulatory ability of chicks, while habitat selection reflects a compromise between diurnal habitat needs and behavioral adaptations that reduce exposure to nocturnal predators.
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Vol. 76 • No. 2