Life history characteristics and habitat quality of flammulated owls (Otus flammeolus) in Colorado.

摘要

I determined the life history characteristics and the components of habitat quality in a Colorado population of Flammulated Owls (Otus flammeolus ) in a 19-yr study. The owl is a small, monogamous Neotropical migrant that nests in mature conifer forests in western North America, and is considered sensitive by the USDA Forest Service. Conservation planning is limited by lack of data regarding the owl's population dynamics and habitat requirements. I assessed population dynamics based on density, territory fidelity, dispersal, survival, and reproduction of the owls. Most owl territories were constant in time and space despite turnover of individuals. Density of breeding pairs showed little annual variation. Up to 70% of territories were occupied annually by bachelor males, suggesting that females have lower survival. Compared to other North American owls, Flammulated Owls have a small and unvarying clutch size, high nesting success, and a long breeding lifespan, indicating they have a life history similar to larger owls.; Territory fidelity was male-biased, as it is with most birds, and pairs rarely divorced. Most breeding dispersals were by females that moved one or two territories away from their original territories. However, females whose nests failed the previous year had lower return rates to the study area than females whose previous nests were successful. Dispersal distance may be bimodal with females dispersing longer distances after nesting failure and shorter distances after successful nests. Females dispersed to territories where total productivity during the study was higher than on original territories, suggesting they assessed territory quality before dispersing.; Characteristics of high-quality breeding habitats were determined by correlating long-term demographic parameters of owls with habitat characteristics on their territories. Territories differed significantly in total years they were occupied by breeding pairs and in total productivity. Availability of cavity-trees for nesting determined where owls established territories, while forest type and structure determined whether a territory was more often occupied by breeding pairs or bachelor males. High-quality breeding habitat for Flammulated Owls was characterized as mature, open stands of ponderosa pine ( Pinus ponderosa) mixed with Douglas-fir (Pseudotsuga menziesii ) with sufficient cavity-trees for nesting.