Birds of a feather don’t always flock together: variation in molt origins and movement patterns of winter finches in Ontario

Abstract

For irruptive or facultative migrants in the subfamily Carduelinae, the winter finches, seasonal movements are extensive but have been poorly described in North America. We used stable hydrogen isotope measurements of feathers (δ2Hf) collected in three regions in Ontario, Canada, during the winters of 2014–15 and 2015–16 to infer potential breeding origins of four species. We also deployed color bands to better understand migratory movements within and across winters. Values of δ2Hf differed by age, sex, and capture location both within and among species. Predicted breeding origins of wintering evening grosbeaks (Coccothraustes vespertinus) and pine grosbeaks (Pinicola enucleator) were largely from northwestern North America, suggesting a predominately west–east pattern of seasonal movements. Common redpolls (Acanthis flammea) and hoary redpolls (A. hornemanni) largely originated from the High Arctic or western Canada, suggesting predominantly north–south seasonal movements. Grosbeaks were most often recaptured or re-sighted at the same capture location between winters. Recaptures and observations of color-banded redpolls only occurred within a winter and mostly at the same capture location. Our results document the first linkages between potential breeding and wintering sites for a large number of individual winter finches during two successive winters. Observed variation in breeding origins and movement patterns suggests each species employs a different migration strategy; therefore, future research and conservation efforts might be more beneficial if directed at individual species of winter finch.