SCAVENGING OF WATERFOWL CARCASSES BY BIRDS IN AGRICULTURAL FIELDS OF BRITISH COLUMBIA

Abstract

Abstract In the Fraser River Delta, scavenging of poisoned waterfowl by raptors during winter has led to secondary anticholinesterase poisoning. During the winters of 1996 and 1998, we used still and video photography to examine scavenging activity on waterfowl carcasses in agricultural fields. Carcass discovery was rapid for both study years; all but two of 54 carcasses were found within 72 h, and 77.8% were found within 24 h (primarily in the first 12 h after sunrise). Single duck carcasses attracted a mean of 16.6 individual scavengers (range 0–79). Seven different species fed on a carcass at least once during 1998, with Bald Eagles (Haliaeetus leucocephalus) and Northwestern Crows (Corvus caurinus) being the most common scavengers. In 1996, Bald Eagles arrived first in 26.7% of the trials. In 1998, Northwestern Crows arrived first in 50.0% of the trials with Bald Eagles and Northern Harriers (Circus cyaneus) each arriving first in 16.7% of the trials. Results demonstrate that individual poisoned duck ...