Noordhuis R. & Spaans A.L. (1992) Interspecific competition for food between Herring Larus argentatus and Lesser Black-backed Gulls L fuscus in the Dutch Wadden Sea area. ARDEA 80 (1): 115-132

Since the late 1960s, breeding numbers of Herring Larus argentatus and Lesser Black-backed Gulls L. fuscus on Terschelling, Dutch Frisian Islands, have risen dramatically, while the ratio between these numbers has changed in favour of the Lesser Black-back (1966-69: < 9000 pairs of large gulls, < 10% Lesser Black-backs; 1985-87:30 000 pairs, 45%). This was paralleled by a change in the diet of the Herring Gull during the reproductive period. Compared with the 1960s, the proportion of marine invertebrates has significantly increased, while the proportion of fish has decreased. Total annual numbers of pellets and faeces with remains of marine fish (to a great extent specimens discarded by fishing boats off the island) dropped to 14% of those in the 1960s. The occurrence of freshwater species increased to a large extent during the period involved, but the rise of this group in the diet could not fully compensate for the decline of marine species in the diet. Lesser Black-backed Gulls still ate primarily marine fish. Species and sizes taken in the 1980s were almost the same as taken by Herring Gulls a few decades ago. Since Lesser Black-backs are more manoeuvrable behind fishing boats than Herring Gulls, it is suggested that the former have forced the latter to concentrate on other food resources. The change in feeding habits has considerably contributed to the Herring Gull's decrease in breeding success (and possibly also in other breeding parameters) which has taken place since the late 1960s.