CONSERVATION OF GULL AND TERN COLONY SITES IN NORTHEASTERN ITALY, AN INTERNATIONALLY IMPORTANT BIRD AREA

River deltas are the focal breeding areas in the Mediterranean region for larid seabirds, but they are being severely altered. The Po Delta is of international importance for Mediterranean and Slender-billed Gu lls and for Gull-billed, Sandwich, Common and Little Terns, but their vulnerable breeding sites are still unprotected. no conservation schem e has been proposed for Mediterranean seabirds, despite the vulnerabil ity of several species, and the protection of only a limited number of colonies has been undertaken. We propose the following specific guide lines for the conservation of the gull and tern colonies in the Po Del ta, based upon a decade of research on habitat requirements and on sev eral vulnerability factors: (1) In the lagoons, necessary measures wil l include protection from human disturbance, active management against erosion of a complex of islets, maintenance of the habitats preferred by each species, and creation of new islets to increase habitat avail ability, especially for the terns; (2) The habitat preferred by each s pecies of conservation concern, islets with bare ground or with 30-100 % cover of vegetation lower than 20 cm, should be maintained in these lagoons. In particular, islets from 0.1 to 0.8 ha, with every reduced cover, and far from other lands, should be provided for Little Terns. Islets larger than one ha and with a high grass cover, preferred by Ye llow-legged Gulls, should be avoided in order to repel this predatory gull. In the main lagoon, the Valli di Comacchio, the existing 26 isle ts should be doubled in number and the new islets should have characte ristics suitable specifically for the terns, which may be limited by h abitat availability; (3) On the outer beaches of the delta, the declin ing population of Little Terns should be protected from human disturba nce by temporary reserves on their colony sites.