In the last decade, geolocators have been implemented to track birds and have provided insights into the migration patterns of small birds not previously available. These devices have been assumed to have minimal impact on survival, although formal survival analyses are often not conducted when geolocators are used. We deployed geolocators on 29 Cliff Swallows (Petrochelidon pyrrhonota) and compared their survival rates over 2 subsequent seasons to 95 birds caught at the same time and site but that had standard aluminum bands only. We recovered 1 geolocator with usable data. The migratory track for this bird indicated stopover behavior, more rapid movement in spring than in fall, and significant over-water travel during spring migration. We found that birds with geolocators had an annual survival probability of 0.07, compared to 0.60 for birds without geolocators. Although this result should be interpreted with caution due to small sample sizes, it suggests that geolocators may affect survival of small aerial insectivore species. Geolocators provide invaluable information on migratory routes of birds, but the effects of geolocators on survival should be further studied.

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