Natural history traits associated with detecting mortality within residential bird communities: can citizen science provide insights?

Cat predation of birds in residential landscapes is ephemeral, unpredictable, and spatially dispersed, and thus requires many person-hours to observe. We sought to identify whether specific behaviors, traits, or feeding ecologies of birds contribute to their probability of cat-caused mortality around residences across temperate North America. In addressing this question, we evaluated citizen science data with respect to peer-reviewed species accounts (Birds of North America, BNA). Using information on cat predation from the BNA, we found that species that glean their prey from the ground or breed in nest boxes were three times more likely to be depredated by cats, while birds that hawk were over two times less likely to become cat prey than would be predicted by random chance. Data from citizen science sources also showed that birds using nest boxes had increased susceptibility to cat predation, as did those that use feeders and that glean from foliage. We caution that observations of predation by citizen science volunteers may be biased towards detection at feeders. Future research should focus on developing volunteer survey techniques for improving estimates of bird mortality rates and sources.

Mortality of Western Burrowing Owls ( Athene cunicularia hypugaea) Associated with Brodifacoum Exposure.

Western Burrowing Owls ( Athene cunicularia hypugaea) frequently occupy periurban areas, where they may be exposed to pest control agents. This short communication describes necropsy findings and detected brodifacoum rodenticide levels for four Western Burrowing Owls in Lake Havasu City, Arizona, US, 2013-15. Levels detected ranged from 0.077 mg/kg to 0.497 mg/kg. Brodifacoum, one of several second-generation anticoagulant rodenticides recently removed from the general consumer market, is still available for use by licensed pesticide applicators. Despite recent regulatory actions, second-generation anticoagulant pesticides continue to threaten predatory species in periurban areas.