Feeding success and relationships of some species ofwaterbirds in the «Valli di Comacchio» (ltaly)

BIDDAU L.

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Abstract:

The feeding success of Black-headed gull, Cornrnon tern and Little egret was studicd in the \"Valli di Comacchio\" lagoon (northeastern Italy), both in presence and abscnce of intra and interspecific interactions. Sometimes gulls and terns feed on the same areas and on particular occasions aggregate with other waterbirds, but little is known about the fccding success and behavioural interactions among thern. The aim of this work was to evaluate the interactions and the feeding success of gulls and terns foraging sintopically with Little egrets. The Little egret had a very high feeding success, but the intraspecific territorialism strongly reduced the time available to fish. The Cornmon tern had difficultics to dive because of the presence of Black-headed gull swimming in the water. The gull was equally successful both in presence and absence of intra and interspecific competition. Then, the observed feeding rate were highcr than data frorn literature; this let to suppose that the birds were attracted by a favourable food supply. I suggest that the observed species are independently attracted to a rich food source.