Can Offspring Sex Ratios Help Explain Patterns of Female-Biased Road Mortality in Barn Owls?
Additional Funding Sources
This research, conducted at the Raptor Research Experiences for Undergraduates site, was supported by the National Science Foundation under Grant No. DBI-1852133 and by Boise State University.
Presentation Date
7-2019
Abstract
Wildlife-vehicle collisions (WVC) kill billions of birds globally, and rates of WVC are particularly high for Barn Owls (Tyto alba). One of the world's highest Barn Owl road mortality rates occurs along I-84 in Idaho, U.S.A. Interestingly, dead females typically outnumber males. Boves and Belthoff (2012) reported 1.4 times more dead females in Idaho, and females outnumbered males by 2.8 times in California (Moore and Mangel 1996). One possible explanation for this pattern is that if both sexes are equally vulnerable to road mortality, females may simply outnumber males in the population and thus are killed in proportion to their abundance. A population skewed towards females could result if Barn Owls produce more daughters than sons through reproduction. We tested this hypothesis that female-biased sex ratios observed in WVC involving Barn Owls in s. Idaho during 2019, captured adn counted nestlings, and obtained blood samples for DNA confirmation of nestling sex. Our poster presents overall sex ratio of nestlings as well as average sex ratio per brood for approximately 40 nests to test the hypothesis that more females than males are produced.
Can Offspring Sex Ratios Help Explain Patterns of Female-Biased Road Mortality in Barn Owls?
Wildlife-vehicle collisions (WVC) kill billions of birds globally, and rates of WVC are particularly high for Barn Owls (Tyto alba). One of the world's highest Barn Owl road mortality rates occurs along I-84 in Idaho, U.S.A. Interestingly, dead females typically outnumber males. Boves and Belthoff (2012) reported 1.4 times more dead females in Idaho, and females outnumbered males by 2.8 times in California (Moore and Mangel 1996). One possible explanation for this pattern is that if both sexes are equally vulnerable to road mortality, females may simply outnumber males in the population and thus are killed in proportion to their abundance. A population skewed towards females could result if Barn Owls produce more daughters than sons through reproduction. We tested this hypothesis that female-biased sex ratios observed in WVC involving Barn Owls in s. Idaho during 2019, captured adn counted nestlings, and obtained blood samples for DNA confirmation of nestling sex. Our poster presents overall sex ratio of nestlings as well as average sex ratio per brood for approximately 40 nests to test the hypothesis that more females than males are produced.
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