General wintering, breeding, and migratory patterns are documented for most species found in North America (Rodewald 2015), but not lesser black-backed gulls. The concentration of this species’ North American population during winter in Pennsylvania, its recent establishment, and the rapid growth in the population provide a unique opportunity to gain fundamental knowledge that may help guide future management decisions
Pennsylvania has been a central location for wintering lesser black-backed gulls in North America, with an average 33% of all North American records found during winter counts from 1996–2006 (Hallgrimsson et al. 2011). Published reports speculate that lesser black-backed gulls from Greenland winter primarily in the Iberian Peninsula and northwest Africa. However, increasing numbers along the Atlantic coast of North America suggest that perhaps a substantial part of the population winters in Canada and the USA (Hallgrimsson et al. 2011).
Although the lesser black-backed gull has been the subject of many color-banding studies, with 91 such programs registered in Europe in 2011 (Raes 2011), only 2 have been found in North America, confirming that at least some lesser black-backed gulls seen in America originate in Iceland and the Netherlands. With only two recoveries, it is impossible to estimate how much each population contributes to the American wintering population, but the much lower number of color-banded birds in Iceland suggests that this source population may contribute more individuals (Hallgrimsson et al 2011). Few birds regularly move between North America and Europe. Investigating the movements of lesser black-backed gulls found in Pennsylvania will improve our understanding of the potential risk of disease transmission posed by this recent winter resident. Understanding these movements will better inform any management decisions before they are made, rather than after they are implemented.