text: Distribution and populationThe Pomarine Jaeger breeds in the far north of Eurasia and North America. It is a transequatorial migrant, mostly wintering between the Tropic of Cancer and Tropic of Capricorn and along the coastlines of Australia and Argentina1. Population justificationIn Europe, the breeding population is estimated to number c.20,000-50,000 breeding pairs, equating to c.60,000-150,000 individuals (BirdLife International 2004). Europe forms 5-24% of the global range, so a very preliminary estimate of the global population size is c.250,000-3,000,000 individuals, although further validation of this estimate is needed. National population estimates include: < c.1,000 individuals on migration in Taiwan; c.50-1,000 individuals on migration and c.50-1,000 wintering individuals in Korea; c.50-10,000 wintering individuals in Japan and c.100-100,000 breeding pairs and c.50-10,000 individuals on migration in Russia (Brazil 2009).Trend justificationThe population is suspected to be stable in the absence of evidence for any declines or substantial threats.EcologyThis species is marine outside the breeding season, remaining somewhat coastal, especially in upwelling regions of the tropics and subtropics. Whilst breeding it specialises on catching lemmings which frequently constitute over 90% of their diet, also feeding on young waders and gamebirds, bird eggs, carrion. In winter it takes fish, sometimes by kleptoparasitism, small seabirds, and scavenges on carrion. Breeding begins in June at scattered sites across the tundra where lemming concentrations are high. Individuals are highly territorial. Outside the breeding season it migrates south including long migrations over land (del Hoyo et al. 1996).