Merlin predation on wintering Dunlins: Hunting techniques, success rates, and the escape tactics of Dunlins
Buchanan, J.B., C.T. Schick, L.A. Brennan, and S.G. Herman. 1988. Merlin predation on wintering Dunlins: Hunting techniques, success rates, and the escape tactics of Dunlins. Wilson Bulletin 100:108- 118.
ABSTRACT.-Interactions between Merlins (Falco columbarius) and Dunlins (Calidris alpina) were studied at estuarine areas in western Washington during winter, 1979 to 1985. Twenty-five of 111 hunting flights by Merlins were successful (22.5%). Five of seven capture attempt techniques were used successfully with a success rate of 4.9%. The most common capture techniques were the stoop at a flock and the chase of an individual isolated from the flock. Most hunting flights (54%) lasted less than 1 min, but hunts of over 5 min were observed (10%). Hunting success rates varied little with the duration of the hunting flight or the size of the Dunlin flock initially targeted. Success rates for hunting flights by Merlins were much higher in Washington (22.5%) than reported from California (12.5%); these higher rates may be the result of a functional response by Merlins in Washington. Dunlins exhibited three distinct types of synchronized predator evasion flights. Dunlins isolated from flocks were often pursued and captured. The most common evasive measure used by isolated birds was a lateral dodge executed while in linear flight away from the flock. Received 5 June 1987, accepted 15 Oct. 1987.