Sabine's Gulls Xema sabini Outside of their Main Wintering Areas are not Necessarily Vagrants

We reviewed published and unpublished ‘vagrant’ (herein referred to as ‘unusual’) records of Sabine’s Gull Xema sabini worldwide and discuss these records according to age, marine productivity/fishing grounds, and migration corridors. Of the 151 unusual records, 135 (89%) were in or near areas with high productivity and/or known fishing grounds; 10 out of 14 documented records were young birds in their first or second migration, and the ‘unusual’ areas identified in this study could have been reached through known migration pathways used by other bird species. The fact that the majority of records are associated with productive/fishing zones (and are also in areas with low or no at-sea effort for bird surveys), and that juveniles and young adults typically migrate further, suggests that some individuals may search for productive areas for wintering outside of the main, or well-known, destinations. Our findings suggest that at least some individuals of Sabine’s Gull, rather than being ‘disoriented’, might be in genuine areas of migration corresponding to their life stage, therefore expanding the known distribution range of this species.