Where Do Songbirds Go to Die?

One afternoon in May 2008, a graduate student named Pat Kramer was in northwestern Pennsylvania catching purple martins. The bird, a large swallow that nests in artificial birdhouses across North America, is a well-studied species. But one particular purple martin Kramer and some fellow researchers from York University caught was about to revolutionize ornithology.

Kramer let an exclamation mark creep into his otherwise staid field notebook when he found it: “At 2:45p.m., Evelina captured Yellow 2551 in WH-43!”

Yellow 2551, the identification code assigned to this martin, was wearing a geolocator, a small device that uses a light sensor to calculate latitude and longitude and track a bird’s movement over time. The geolocator had traced this female martin’s migratory journey to Brazil and back via the Yucatan Peninsula. In doing