BEEKMAN JH & PLATTEEUW M (1989) Great Black-backed Gulls Larus marinus try to feed on Great Crested Grebes Podiceps cristatus. LIMOSA 62 (1): 46-47.

Great Black-backed Gull Larus marinus Great Crested Grebe Podiceps cristatus On three occasions in February 1988 it was observed that Great Black-backed Gulls attacked foraging Great Crested Grebes with the apparent intention to kill them for food. This occurred just in front of sluices in Lelystadhaven (Lake IJsselmeer, Netherlands) which had been letting out large amounts of water, resulting in an increased fish density (mainly smelt Osmerus eperlanus). These densities attracted large numbers of fish-eating birds, among which Smews Mergus albellus, Goosanders M. merganser, Cormorants Phalacrocorax carbo and Blackheaded Gulls Larus ridibundus as well as grebes. The attacks on the grebes were mainly directed to grab the birds by the neck and try to lift them out of the water. Actual catches were not seen. Great Black-backed Gulls are known to kill adult birds as well as chicks for consumption. In these particular circumstances it is suggested that the main reason for picking out the Great Crested Grebes rather than any of the other species present was that the latter were all fishing in social groups (while the grebes fished solitarily), thus making it more difficult to direct the attacks. This way, an advantage of social fishing in diving and swimming birds, might be better protection against direct predation by Great Black-backed Gulls.

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