First year-round movement tracking of the Mediterranean Gull (Ichthyaetus melanocephalus) in Europe: insights and conservation recommendations for declining population

Abstract This study examines the Mediterranean Gull ( Ichthyaetus melanocephalus ), utilizing GPS/GSM transmitters year-round for the first time on this species. The research covers habitat use, migration patterns, and breeding behaviors, tracking 19 birds captured at breeding colonies in Poland. To capture the birds and fit transmitters, we selected representative locations: islands in dam reservoirs, gravel pits, rivers, and lakes. Mediterranean Gulls nested mainly in colonies of Black-headed Gulls ( Chroicocephalus ridibundus ). By tracking birds with transmitters, we identified nine additional breeding sites within Poland, the Czechia, and Germany. We determined the mean length of phenological periods: breeding (76, April 10–June 26), autumn migration (11, June 26–July 7), winter (261, July 5–March 23), and spring migration (18, March 23–April 10). According to residence sites analysis, cropland was the most frequently used habitat during breeding (52.9%), while the open sea was predominant in winter (25.8%). We identified key wintering areas: the English Channel, the Utrecht–Antwerpen area, the North Sea coast, and the Irish Sea coast. One individual wintered along the coast of Portugal and near Malaga in Spain. An interesting discovery was the longer spring migration than autumn what involved visits to multiple potential breeding sites, leading to the mapping of a network of potential breeding areas. This underscores the need for proactive habitat protection and comprehensive conservation strategies. Given the Mediterranean Gull’s migratory behavior and lifecycle, the study advocates for it as a model for conserving migratory waterbirds.