Rate of removal of bird carcasses in arable farmland by predators and scavengers

Studies requiring carcasses to be retrieved to detect mortality and its causes in wildlife can be difficult to interpret due to removal of carcasses by scavengers. This paper describes two linked studies measuring rate of removal of carcasses from farmland in the UK, carried out to inform the results of a pesticide study involving carcass searching. In winter, 6% of carcasses had been removed 24 h after placement, and 32% had been removed 96 h after placement; wild bird carcasses were removed significantly faster than those of artificially reared birds. In summer, 76% of carcasses had been removed 24 h after placement and 91% after 96 h. A literature review of similar studies is given. Carcass removal rates by predators and scavengers appear to vary widely between sites and seasons, and may be high. If the results of studies involving carcass searches or surveillance are to be interpreted correctly, carcass removal rate by scavengers should be measured under similar conditions to, and contemporaneous with, those under which mortality is expected to occur.