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Publication Date

9-1-2009

Abstract

An unusually cold and wet weather event occurred in San Marcos, Texas, USA during January 2007, resulting in large numbers of dead Cave Swallows (Petrochelidon fulva). Surveys of all known roosting areas within the city limits revealed a complete die-off of Cave Swallows; we collected 123 dead swallows from eight roost sites. Measurements of dead swallows indicated the birds that died along Interstate underpasses during the cold spell had smaller bodies yet were heavier than those in a parking garage. Thermometers placed at the two roosting site types revealed that the underpasses were 5°C colder than the parking garage site during the coldest part of the day. Extreme temperatures may have affected Cave Swallows using underpasses more so than swallows roosting in the parking garage. Higher post-mortem body condition (log mass/log tarsus length) may suggest death from starvation for birds in garage and cold exposure for birds under bridges. Future studies that examine environmental differences between multiple roost sites may provide stronger support for our findings and have implications for northward range expansions of species in the face of global climate change.

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