Ecology, habitat use, and probability of detection of Flammulated Owls in the Boise National Forest

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This thesis consists of three chapters presenting results of research on the ecology, habitat selection, and probability of detection of the Flammulated Owl (Otus flammeolus) in central Idaho. Objectives (as covered in the chapters, respectively) were to 1) document details of breeding season chronology, mortality, interspecific interactions, and movement patterns; 2) investigate patterns of habitat selection at multiple spatial scales; and 3) describe changes in detectability of owls by broadcast surveys over the course of the breeding season. Field work was conducted from May through August 2005 and 2006 in the Lowman RD of the Boise NF. This study was the first radio-telemetry study of the species in Idaho. The owls arrived on breeding grounds in the first week of May both years, and the mean date (± SD) for laying was 10 June ± 11.3 d, for hatching was 3 July ± 10.8 d, and for fledging was 25 July ± 10.5 d. Mortality was approximately 20% over the breeding season for adults and approximately 37% for juveniles between fledging and independence. Between 23 and 46% of males were not paired with a female. At the landscape level, owls selected south and east-facing aspects, middle to upper slopes and ridges, and areas of intermediate forest cover. At the home range scale, owls selected areas with higher density of standing dead trees (snags) but showed high variability in use of other forest characteristics. Owls selected large ponderosa pine trees for day roosts, and when owls roosted in Douglas-fir trees, they often selected medium-sized trees. Overall results suggest high variability of habitat use at scales below the landscape scale. Probability of Flammulated Owl detection was 100% during the pair-bonding and incubation periods of the breeding season, and afterward the rates steadily declined to a low of less than 15% during the post-fledging period. Detectability of paired males showed a gradual decline following hatching of eggs, whereas detectability of unpaired males dropped sharply during this same time period.

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ELECTRONIC FILE - Zoology