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

Raptor predation on waders was studied by direct observation of raptors hunting a known wader population and subsequent recovery of dead waders. In each of three winters, raptor predation was shown to be the most significant cause of mortality in most small wader species. Sparrowhawks Accipiter nisus, Merlins Falco columbarius and Peregrines F. peregrinus attacked waders with a success rate of 11.6%, 8.8% and 6.8%, respectively. Most waders attacked or found dead were Redshank Tringa totanus and Dunlin Calidris alpina; most were killed by Sparrowhawks. Kleptoparasitism of raptors carrying prey by Carrion Crows Corvus corone significantly increased the winter mortality of some waders. Redshank populations were most affected by raptor predation; over 50% of the total population (which was found to be closed during most of the winter) and over 90% of the juvenile population were taken in two winters: juveniles were more likely to be killed by raptors.