Effect of shore width on the predation rate of artificial wader nests

Destruction and deterioration of breeding habitats are considered primary factors contributing to population declines of most threatened waders of the Western Palaearctic. On the Baltic coasts, the habitat changes have usually been linked with the cessation of grazing and haymaking on the shore meadows followed by overgrowth and reduction of the open area. Many waders of open and short-vegetated habitats have almost disappeared in certain areas. These species include Dunlin Calidris alpina, Temminck's stint Calidris temminckii and ringed plover Charadrius hiaticula. We tested the idea that reduction of the width of the shores has in part caused the decline of waders of open habitats on the Baltic coasts. The hypothesis that the predation rate of wader nests is higher on narrow shores than on wide ones was tested experimentally by comparing predation rates on artificial ground nests put out on narrow and wide shores. We put out 160 artificial nests on 16 shore meadows near the town of Oulu, 65 degree N, 25 degree E, northern Finland, in late May 1992. All sites resembled Temminck's Stint and Ringed Plover habitats. The study area contained breeding Temminck's Stint, Ringed Plover and Dunlin. For a description of the typical dune vegetation of the research area, see Alestalo (1983). Our conclusion is that the probability of an artificial nest with one egg being located accidentally by a predator did not depend on the shore width. Instead, the suggested higher rate of the predation pressure on natural nests on narrow shores might be linked with the parental behaviour at or near the nest.