Strong Migratory Connectivity in a Declining Arctic Passerine

Determining how animal populations are linked in space and time is important for identifying factors influencing population dynamics and for effective conservation and management. Arctic-breeding migratory passerines are declining and at risk due to forecasted climate change, but are a challenge to monitor due to their inaccessible breeding locations, long-distance migration routes and small body size. For the first time, we combine sub-gram geolocator technology and stable-isotope analysis with mark-recapture (banding) and citizen science data to determine patterns of migratory connectivity for multiple populations of a declining North American Arctic-breeding passerine, snow bunting (Plectrophenax nivalis). We show strong evidence for an east-west parallel migratory system, with Hudson Bay acting as a migratory divide. While band recoveries suggest strong migratory connectivity among eastern wintering populations (more than 95% of band recoveries reveal connections between western Greenland and eastern North America), novel application of geolocators and stable-hydrogen isotope analysis to a Canadian breeding population revealed a high degree of migratory connectivity within western North American wintering populations. Our results also show distinct differences in migratory distance between eastern and western populations, and illustrate how applying multiple techniques can effectively be used to track migration patterns of remote populations. Differences in annual distribution and migratory distance suggest that separate consideration of eastern and western wintering populations may improve future conservation and management efforts for this species.