Spatial distribution, demography and breeding biology of the Falklands skua of Sea Lion Island, Falkland Islands (2013-2019)

The dataseries comprises of data on nest location and spatial distribution, nesting habitat, demography, and reproductive success of the Falklands skua (Stercorarius antarctica antarctica) at two location in Sea Lion Island: 1) the lodge area, close to gentoo penguin colonies, and 2) the west end of the island, including the Sheffield Memorial area, close to the rockhopper penguin and king cormorants colonies. The data were collected during the 2013-2019 breeding seasons. Density and spatial distribution of nests in these two areas were quite different. In 2015-2016 a notable increase in the number of skua nesting pairs compared to the previous season was observed. Breeding success was high, and higher than the one reported for other breeding areas in the Falklands. On the contrary, in recent seasons a notable reduction in the number of skua nesting pairs and in the total breeding success of the population compared to the previous season was noted. The reduction in breeding success was stronger in the west end area. The reasons of this general reduction in success, and of the differential impact on the two different breeding areas, are unknown and deserve further investigation. Until now, effect of striated caracara predation, that was previously suggested as a potential regulator of skua demography, have been excluded. Further information is available on the research group website, www.eleseal.org.