Avian Nesting Ecology in Small Even-Aged Aspen Stands

Observed versus expected numbers of total nests (all species combined) and those of towhees and catbirds differed of stand age and distance from an edge but was inversely related, with higher nests more susceptible than lower nests to predators.

Abstract

I examined abundance, location, and success of avian nests from June through August, 1985-87, in small (1 ha) even-aged aspen (Populus spp.) stands on a 240-ha study area managed as ruffed grouse (Bonasa umbellus) habitat in central Pennsylvania. Ninety-five nests of 14 species, mainly rufous-sided towhee (Pipilo erythrophthalmus) (28.4%) and gray catbird (Dumetella carolinensis) (24.2%), were located. Observed versus expected numbers of total nests (all species combined) and those of towhees and catbirds differed (P < 0.05) among stands of 3 age classes; the majority of total (91.6%), towhee (92.3%), and catbird (100%) nests was found in stands ≤10 years old. Observed versus expected numbers of both total and towhee nests did not differ (P > 0.05) in relation to distance from an edge. However, observed numbers of catbird nests varied (P < 0.05) from what I expected with respect to distance from an edge; most (95.7%) were located ≥10 m from an edge. Young were fledged at 52.6% of the total nests. Nesting success was independent (P > 0.05) of stand age and distance from an edge but was inversely related (P < 0.05) to height of nests. Higher nests (>0.5 m above ground level) were more susceptible than lower nests (≤0.5 m) to predators.