THE EFFECTS OF RAPTOR PREDATION ON WINTERING WADER POPULATIONS AT THETYNINGHAME ESTUARY, SOUTHEAST SCOTLAND

Raptor predation on waders was studied by direct observation of raptor s hunting a known wader population and subsequent recovery of dead wad ers. In each of three winters, raptor predation was shown to be the mo st significant cause of mortality in most small wader species. Sparrow hawks Accipiter nisus, Merlins Falco columbarius and Peregrines F. per egrinus attacked waders with a success rate of 11.6%, 8.8% and 6.8%, r espectively. Most waders attacked or found dead were Redshank Tringa t otanus and Dunlin Calidris alpina; most were killed by Sparrowhawks. K leptoparasitism of raptors carrying prey by Carrion Crows Corvus coron e significantly increased the winter mortality of some waders. Redshan k populations were most affected by raptor predation; over 50% of the total population (which was found to be closed during most of the wint er) and over 90% of the juvenile population were taken in two winters: juveniles were more likely to be killed by raptors.