Response to Streby and Kramer: Additional considerations for explaining differences in return rates of geolocator-tagged and control Cerulean Warblers

Abstract

Our recent manuscript investigated geolocator-tagging effects on a small migratory warbler. Streby and Kramer (2017) suggest that a year effect may have been masked by our unequal sample sizes between years. They also argue that the difference in return rate between our geolocator-tagged and control birds was likely due to differences in harness styles used between years. We agree with their comment regarding the possibility that a year effect could have been masked by our unequal sample sizes. However, it is not possible to draw reliable conclusions from our data as to why we observed a reduced return rate for geolocator-tagged birds compared with color-banded controls, and attempts to do so are mere speculation. We also point out that both harness styles used in our study have been employed by a number of researchers who observed no reduced return rates for geolocator-tagged birds, including other species of parulid warbler. Researchers desiring to illuminate potential harness style effects on return rates should use large sample sizes of each harness type, in the same year, and search for all geolocator-tagged and control birds with equal effort.