Several studies have emphasized the importance of postfledging survival when estimating avian population growth rates, yet high variation exists in reported estimates. Mechanisms influencing postfledging survival also remain poorly understood. The influences of local habitat quality and landscape context on postfledging movements also remain largely undocumented. We measured daily postfledging survival and movements in Ovenbirds (Seiurus aurocapilla) in selection cut plots (30–40% basal area removal) and controls. Specifically, we tested predictions from the “concealment” hypothesis (higher survival/shorter movements with increased fledgling concealment), “body condition” hypothesis (higher survival/longer movements with increased body mass), and “predator abundance” hypothesis (higher survival/shorter movements when predator abundance is low) by monitoring fledgling survival (n = 55) and movements (n = 41) during the first 2 weeks postfledging. Fledglings were monitored over 2 breeding seasons in 5 pairs of experimental plots, 25 ha each (1 control and 1 treated plot per pair), located in mature hardwood stands. We found support for an effect of predator abundance on survival (i.e. effects of plot-level abundance of red squirrels and year). Models including habitat variables or body mass received weak support. A positive trend for effect of body mass on movement between successive locations was found but no evidence for an effect of predator abundance or habitat variables. These findings indicate that spatiotemporal variation in predator abundance was a key factor determining daily postfledging survival rate in this Ovenbird population; however, predator abundance did not influence movement rate, suggesting that fledgling Ovenbirds were unable to respond to predation risk.
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Vol. 116 • No. 1