A recent paper published in The Condor: Ornithological Applications by Raybuck et al. (2017) described the results of an analysis of potential effects of light-level geolocators on reproductive parameters and apparent annual survival of Cerulean Warblers (Setophaga cerulea). In a comparison of geolocator-tagged birds and color-banded control birds, the authors reported no discernible differences in several standard reproductive parameters, but a significant difference in apparent annual survival. Here, we show that the reported overall geolocator effect on annual survival may have obfuscated a large effect in one year, when one geolocator model and harness method were used, compared with no effect on annual survival in the second year of their study, when a different geolocator model and harness method were used. These more nuanced results suggest that Raybuck and colleagues may have identified variation in effects between geolocator marking methods for Cerulean Warblers, rather than a general geolocator effect on annual survival.
PUBLICATION AVAILABLE AT: http://doi.org/10.1650/CONDOR-17-111.1