Habitat selection and nesting association in four species of Charadriiformes in the PoDelta (Italy).

Colony, nest site selection and interspecific associations of four breeding Charadriiformes werestudied in the Po Delta, Italy, in 1991. Physical characteristics (such as length, size, distance from mainlandand other islands, occurrence of small dunes, etc.) of eighteen islands and two peninsulas were considered;random points were selected on the islands, and several parameters (such as distance from the shore, apparentelevation above sea level, vegetation cover, kind of substrate, etc.) compared with those of a similar numberof nest sites. Apart from Yellow-legged Gulls Larus cachinnans, which selected the longest and largest islands,the other species (Oystercatchers Haematopus ostralegus, Kentish Plovers Charadrius alexandrinus a n dLittle Terns Sterna albifrons) did not show particular preferences at this level . With regard to nest site characteristicsof each species, they were often different from random points and, less frequently, from those ofthe other species. Yellow-legged Gulls preferred sites with less sand, higher vegetation cover and tallerplants; the opposite was true for Kentish Plovers. Intermediate characteristics were selected by Oystercatchersand Little Terns. Significant associations were found between Oystercatchers and Yellow-legged Gulls,Oystercatchers and Kentish Plovers, Kentish Plovers and Little Terns. Our study suggests that physical factors(i.e. nest site features) and behavioral factors (association resulting in better protection from predators, or dueto a limited feeding overlap in the nearby intertidal areas) interact in the habitat selection of the four species

Roberto Valle & Francesco Scarton, Ardeola 46(1), 1999, 1-12