McLaren, Ian A. 1981. The incidence of vagrant landbirds on Nova Scotian islands. The Auk 98: 243-257.
Abstract: “Many vagrant landbirds have occurred on Brier, Sable, and Seal islands, Nova Scotia and have produced first records for Nova Scotia or Canada. In counts made on these islands for more than a decade, individuals of western species were relatively more common than in similar counts on islands off northeastern Florida in spring and North Carolina in fall. Western vagrants were more frequent, but much less diverse, on the Florida islands in fall. Recent checklists substantiate the conclusion that vagrant species from remote ranges are more diverse on the Nova Scotian islands than in other localities in eastern North America. The diversity and high incidence of vagrants may be related partly to the convergence of continental windstreams on Nova Scotia during migration seasons. Regional species, however, evidently avoid Sable Island, which is farthest offshore, whereas vagrants from remote ranges are relatively more common there than on the other two islands. This suggests that navigational error by “lost” vagrants is paramount. Weather patterns are examined in association with the earliest vagrants of each season, as these vagrants may have come most rapidly and directly. Southern vagrants may fly past their normal ranges in spring, unassisted by winds. Western species in spring are probably not generally deflected from their normal routes by winds. Western Dendroica spp. in spring in the east may come because of mirror-image disorientation. Southern vagrants are proportionately as common in fall as in spring, and individuals may or may not be wind-assisted in their reverse migrations. Western vagrants are relatively more common in fall than in spring. Some may come directly down-wind on fall westerlies, but their relatively high incidence in Nova Scotia may result from their being swept up the east coast by prevailing southwesterlies. Turn-of-the-century records from Sable Island suggest that vagrancy may have increased among species that have expanded their populations or ranges, especially those of disturbed habitats. Received 16 May 1978, accepted 5 July 1980.”