| Because large proportions of immature birds raised to independence do not survive to breed, it is important to determine whether juvenile survival is limiting population growth. I tracked radio-tagged juvenile Western Burrowing Owls (Athene cunicularia hypugaea) in southeast Alberta from fledging until migration, and recorded higher juvenile survival than that found in two other studies in terminally declining Canadian populations. I also evaluated two styles of radio-tags, necklaces and backpacks, and determined that necklace style tags may negatively affect juvenile survival. Because late season and cohort specific diets are rarely studied, I tracked dispersing adults and juveniles, and dissected pellets collected at their diurnal roost burrows, to contrast prey use. I found that dietary heterogeneity between adults and juveniles resulted principally from differences in biomass of nocturnally active prey, such as rodents and ground beetles, and that juvenile diets were almost predominantly insectivorous. (Abstract shortened by UMI.)... |
