Flight and foraging patterns of lesser black-backed gulls and northern gannets in the southern North Sea

The study focuses on the foraging ecology of two common seabird species of the southern North Sea, lesser black-backed gulls and northern gannets. The spatiotemporal patterns were considered in light of offshore wind farms, representing a recent anthropogenic pressure on the birds' foraging and space use. Flight and foraging patterns of both species were recorded by attaching small GPS data loggers on breeding birds at different German North Sea Islands. Their foraging patterns differed among the six studied breeding colonies and between the sexes, and also indicated a large amount of individual specialisation in foraging behaviour. The vertical flight distribution of lesser black-backed gulls showed that birds flew in the critical heights of the rotor swept areas of offshore wind farms to a certain extent, and thus were likely to collide with offshore turbines, expecially during bad weather conditions. Northern gannets, which are rather inflexible flyers with poor flight manoeuvrability compared to the gulls, largely avoided the offshore wind farm areas, and only crossed those areas where turbines were not installed yet.