Connectivity between breeding sites, wintering areas, and migration routes in Common Terns (Sterna hirundo) breeding in the Western Palaearctic

Abstract

Detailed knowledge about bird migration patterns can enhance our understanding of the evolution of migration and temporal changes in space use throughout the annual cycle. Additionally, as many migratory bird species are experiencing population declines, understanding the connectivity between their spatial distributions during breeding, migration and wintering may enhance our ability to conserve species whose populations are of conservation concern. In this study, we utilized thousands of ringing records collected in Israel (2010–2025) and Europe (1913–2025) to investigate the migration patterns of Common Terns Sterna hirundo breeding in the Western Palaearctic. The ringing records collected in Israel can expand our knowledge of the East Mediterranean–East African (EMEA) flyway of European-breeding Common Terns. We examined the connectivity between breeding sites in Europe and wintering areas in Africa, as well as the two major European–Afrotropical migration routes: the EMEA flyway via the Indian Ocean (typically wintering in eastern and southern Africa) and the East Atlantic flyway via the Atlantic Ocean (typically wintering in western and southern Africa). Common Terns using the East Atlantic flyway predominantly breed in Western Europe, Fennoscandia and the Baltic region, whereas individuals migrating along the EMEA breed in Central and Eastern Europe as well as the Middle East. An overlap zone occurs at the breeding areas in Central Europe and probably also in southern Africa, where Common Terns from both migration routes winter in overlapping areas. Additionally, our findings indicate a pattern of leap-frog migration, in which northern European-breeding populations migrate over longer distances and winter in southern Africa, bypassing the equatorial wintering areas used by southern-breeding populations. We suggest that a preference for coastal habitats outside the breeding season may influence route use and, as a result, also connectivity. These findings expand our knowledge of Common Tern migration routes, highlight the relevance of ringing data for large-scale studies of migratory populations and provide a basis for future research on migratory routes and spatial connectivity between breeding and non-breeding areas.