Bird window collisions link a local urban landscape to continent-wide migratory origins

Abstract

Collisions with buildings are a major cause of anthropogenic bird mortality, yet little is known about the migratory origins of birds killed by window collisions. We used hydrogen stable isotope (δ²H) values to estimate the geographic origins of 129 birds from 13 species that died from window collision on the University of Florida campus between 1997 and 2021. Our objectives were to (1) infer individual origin locations, (2) calculate minimum travel distances by species, and (3) compare variation in migratory origin among species. We analyzed the hydrogen isotope composition of wing feathers and determined likely origin using spatial models of precipitation isotopes across North America. Birds killed on this north-central Florida campus originated from a wide range of latitudes, with some having traveled over 4,000 km. Our findings demonstrate the broad spatial scale of migratory origins linked to localized collision events and emphasize the need to incorporate full annual cycle ecology into mitigation strategies. This study also highlights the value of hydrogen isotopes for tracing movement patterns and informing conservation planning for migratory birds.