Comparing inferences of solar geolocation data against high-precision GPS data: annual movements of a double-tagged black-tailed godwit
Rakhimberdiev, E.; Senner, N.R.; Verhoeven, M.A.; Winkler, D.W.; Bouten, W.; Piersma, T. (2016). Comparing inferences of solar geolocation data against high-precision GPS data: annual movements of a double-tagged black-tailed godwit. J. Avian Biol. 47: 589–596. dx.doi.org/10.1111/jav.00891
In: Journal of Avian Biology. Munksgaard: Copenhagen. ISSN 0908-8857; e-ISSN 1600-048X, more
Annualroutines of migratory birds inferred from archival solar geolocation devices have never before been confirmedusing GPS technologies. A female black-tailed godwit Limosa limosa limosa captured on the breeding grounds in theNetherlands in 2013 and recaptured in 2014 was outfitted with both an Intigeo geolocator and an UvA-BiTS GPS-tracker.The GPS positions show that, after its breeding season in 2013, the godwit flew 2035 km nonstop from the Netherlands tosouthern Spain. It then spent the entire nonbreeding season in the southern part of the Iberian Peninsula before returningto the Netherlands the following spring, stopping for 7 days in the delta of the Ebro River in Spain, and again for a dayin central Belgium. To compare the geolocation and GPS data, we analysed the geolocation data with two open-sourcesoftware packages: one using a threshold method (GeoLight) and the other a template-fit approach (FLightR). Estimatesusing GeoLight, on average, deviated from the individual’s true position by 495.5 ? 1031.2 km (great circle distance withequinoxes excluded), while FLightR estimates deviated by 43.3 ? 51.5 km (great circle distance with equinoxes included).Arrival and departure schedules estimated by FLightR were within 12 h of those determined by the GPS tracker, whereasGeoLight’s estimates were less precise. For the analysed track, FLightR represents an improvement over GeoLight; if truefor other species and conditions, FLightR will hopefully help establish more precise and accurate uses of geolocation datain tracking studies. To aid future improvements in the analysis of solar geolocation data, we also provide the GPS andgeolocation data files together with our R scripts as Supplementary material Appendix 1–6.
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