Investigating methods of geolocator analysis in songbird migration research and their application to the study of a threatened, neotropical songbird
Loading...
Date
2018
Authors
Roberto-Charron, Amélie
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Migration is the least understood phase of a migratory bird’s annual life cycle. Many migratory species are currently experiencing steep rates of population decline. Through direct tracking using new miniaturized light-level geolocators it is now possible to estimate the position of individual songbirds year-round and improve our understanding of factors that could be causing population declines. Geolocators record time and ambient light, and based on these values it is possible to infer the location of an individual. As this technology has developed, so have the corresponding methods of analysis. The objectives of this thesis were 1) to compare qualitatively and quantitatively the three main open source methods of analysis (GeoLight, SGAT and FLightR) for songbird geolocator data. I used data derived from different species where data quality is expected to differ based on habitat and behaviour, and 2) to apply these methods to analyze the geolocator data of a threatened Neotropical migrant, the Canada Warbler (Cardellina canadensis), to identify migration routes and wintering areas. I found that shading of the light-sensor of the geolocator had a detrimental impact on geolocation estimates. I found no effect of analysis method on the variance in longitudinal estimates, but that GeoLight provided more variable latitudinal estimates than SGAT and FLightR. I used FLightR to analyze Canada Warbler geolocator data from three breeding populations (locations, province/state) across the breeding range. During fall migration, individuals from all three locations funnelled through a narrow geographic region (97-99 W) along the western coast of the Gulf of Mexico, with most individuals (72%) arriving at overwintering sites in Colombia. My results highlight the value of conservation of overwintering habitat in Colombia and migration habitat along the western coast of the Gulf of Mexico for these three breeding populations. Regarding my investigation of analysis methods, discrepancies between true and inferred geolocation estimates have the potential to lead to incorrect conservation actions. As such, researchers undertaking geolocator-based studies must have a strong understanding of the capacity and limitations of the technology.
Description
Keywords
Ecology, Geolocator, Songbird, Canada warbler, Migration