Dusky Flycatchers (Empidonax oberholseri) nesting in a mixed conifer-aspen woodland in southern Utah occurred at a breeding density of 0.44 territories/ha. Females began laying first clutches 1–26 June; adults fed nestlings (in renesting attempts) as late as mid August. Mean clutch size was 3.8 eggs in first clutches and 3.6 eggs overall. Incubating females spent 90% of daylight hours on the nest, where they were fed by males 1.1 times/ hour. Incubation lasted 14–16 d; nestlings remained in the nest 15–17 d. Thirteen of 32 nests (40.6%) were successful in producing at least one fledgling, with successful nests producing 2.7 young/nest. Based on exposure, probability of a nest surviving from egg laying to fledging was 0.40. Predation accounted for 84.2% of nest failures; brood parasitism by a Brown-headed Cowbird (Molothrus ater) occurred at one nest.
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Vol. 76 • No. 2