European Herring Gull (Larus argentatus) Science Article 9
The distribution and feeding range of Herring Gulls and Lesser Black-backed Gulls breeding on the Dutch Wadden Sea islands were assessed, using the results of ship-based surveys in the southern North Sea. The occurrence of both species in association with commercial fishing vessels is described in relation to distance to the coast and distance to the colonies. The feeding range of Lesser Black-backed Gulls (95% of all birds within 135 km of the colony) was considerably larger than that of Herring Gulls (95% within 54 km), and this difference could not be explained by differences in flight capacities. Feeding success and vulnerability to robbery of both species as scavengers at fishing vessels are described. Neither the vulnerability to robbery indices, nor the feeding success indices of both species did support earlier suggestions that Lesser Black-backed Gulls may have outcompeted Herring Gulls at (nearshore) fishing vessels. The feeding range of Lesser Black-backed Gulls could not solely be explained by a general avoidance of Herring Gulls near the coast, nor by the presence fishing vessels further offshore in comparison with the coastal zone. It is concluded that the large feeding range was motivated by a third, but unknown factor. The reduction of fisheries near the coast has probably led to a reduction in feeding opportunities for scavengers near the coast.
Camphuysen C.J., ARDEA 83 (2): 365-380.