Estimating geolocator accuracy for a migratory songbird using live ground-truthing in tropical forest
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Author/Creator ORCID
Date
2013-02-06
Type of Work
Department
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Citation of Original Publication
Emily A. McKinnon, Calandra Q. Stanley, et.al, Animal Migration, Volume 1, Pages 31–38, ISSN (Online) 2084-8838, DOI: https://doi.org/10.2478/ami-2013-0001.
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Attribution-NonCommercial-NoDerivs 3.0 United States
Attribution-NonCommercial-NoDerivs 3.0 United States
Abstract
Miniaturized light-level geolocators allow year-round tracking of small
migratory birds, but most studies use calibration only at breeding sites to
estimate geographic positions. Ground-truthing of positions in tropical
habitat is needed to determine how accurate breeding site calibrations (i.e.
sun elevations) are for estimating location of winter sites. We tested the
accuracy of geographic assignments using geolocator data collected from
Wood Thrushes (Hylocichla mustelina) in Central America. For a given light
threshold, sun elevation angle was higher in the tropics than at breeding
sites and also varied significantly at tropical winter sites between wet (OctDec) and dry (Jan-Mar) seasons. However, estimation of Wood Thrush
territory latitude did not differ significantly when using breeding or tropical
dry season sun elevation. Average error in assignment to tropical sites was
365 ± 97 km (0.2-4.4°) in latitude. To obtain the best latitude estimates in
the tropics with geolocators, we recommend using locations during the
dry season where sun elevations are closer to those measured at breeding
sites. We emphasize the importance of longitude in assigning forest birds
to unknown sites; longitude estimates for Wood Thrushes in the tropics
were, on average, within 66 ± 13 km (0-0.6°) of actual longitude. Latitude
estimates were more accurate (180 ± 48 km) when assigning birds to
breeding sites using deployments of geolocators in the tropics. Studies of
species that are territorial in winter could collect more accurate migratory
connectivity data by deploying geolocators at tropical wintering sites.