Widely distributed breeding populations of Canada warbler (Cardellina canadensis) converge on migration through Central America

Migratory connectivity and timing for an at-risk Canadian landbird, Eastern Whip-poor-will (Antrostomus vociferus), from two geographically distant breeding areas

Determining the year-round spatial distributions of at-risk avian migratory species is critical for effective conservation. High-precision tracking enables the identification of distant breeding and nonbreeding areas and their connectivity, as well as migratory routes and associated threats. We GPS-tracked two groups of Eastern Whip-poor-wills ( Antrostomus vociferus (A. Wilson, 1812)) that breed near the northern edge of their range, in Manitoba and northwestern Ontario (“west”), and in southern Ontario (“east”), Canada. The western-breeding birds were also ∼5° of latitude farther north than the eastern birds. We aimed to determine the degree of spatiotemporal overlap between the two groups during fall migration and at tropical wintering sites. We found that western-breeding birds departed earlier on migration than eastern-breeding birds, but we did not detect a difference in arrival timing to wintering sites. The two breeding groups retained spatial structure during migration, until all routes converged to circumnavigate the Gulf of Mexico. Western-breeding birds overwintered at sites farther south than eastern-breeding birds, consistent with a leapfrog pattern of migration. Quantifying the strength of migratory connectivity in at-risk species can be a first step toward defining breeding populations and informing customized conservation strategies throughout the annual cycle.