Offshore structures provide feeding hotspot for seabirds

Man-made offshore structures provide a foraging hotspot for seabirds, according to a new study published online in Communications Biology. These findings help provide a broader understanding of the ecological consequences of establishing such structures offshore.

Surface-feeding seabirds, like terns, rely on turbulence, or shallow upwellings, to feed. Turbulence brings prey closer to the water’s surface, allowing seabirds better access despite being restricted to shallow diving techniques. Offshore man-made structures, built to produce renewable energies, change local water flow systems. Previous research has found that fish can use offshore structures as a refuge. However, the implications for seabird predators have not yet been examined.

Lilian Lieber and colleagues examined the foraging patterns of terns (Sternidae) within 1 kilometre of wake-producing structures: a man-made tidal energy turbine structure, a rock island, and a natural whirlpool structure. The authors observed three times as many birds foraging over the man-made structure. They found that the turbulent man-made wake mixes material throughout the water column, potentially acting as a prey conveyer belt, thereby making prey available for surface foraging predators.

The authors suggest that addition of more offshore structures, and subsequent removal, may have a larger ecological impact than previously thought.