Eastern United States

Trackers may tip a warbler’s odds of returning to its nest

Cerulean warbler
Cerulean warblers wearing geolocators on their backs may be less likely to complete the usual return flight from South America to their breeding grounds in the eastern United States.

Strapping tiny trackers called geolocators to the backs of birds can reveal a lot about where the birds go when they migrate, how they get there and what happens along the way. But ornithologists are finding that these cool backpacks could have not-so-cool consequences.

Douglas Raybuck of Arkansas State University and his colleagues outfitted some Cerulean warblers (Setophaga cerulea) with geolocators and some with simple color tags to test the…