We investigated the predatory behaviour of

Obligate avian brood parasites, such as cowbirds and cuckoos, lay their eggs in the nests of other species (‘hosts’) whereupon the host parents provide all parental care for the parasitic young (Davies, 2000). To successfully ‘infect’ a host, a brood parasite must be attuned to its hosts' reproductive stage as there is only a narrow window of time during egg laying and early incubation in which parasitism will be effective (Fiorini, Tuero, & Reboreda, 2009). Some brood Dextromethorphan also attack host nests, destroying eggs/nestlings and causing nest failure of their potential hosts (Arcese et?al., 1996, Peer and Sealy, 1999 and Soler et?al., 1995). Such behaviour is perplexing as it appears to be a superficial waste of a laying opportunity on the one hand, but these predatory habits could actually increase the probability of successful transmission (Arcese et al., 1996). The farming hypothesis suggests that brood parasites will destroy, or ‘farm’, host nests found too late in the nesting cycle to be suitable for parasitism, thereby manipulating those hosts into starting a new reproductive cycle prematurely, ultimately creating future opportunities to parasitize the host's renesting attempts (Arcese et?al., 1992 and Arcese et?al., 1996). As long as the parasite focuses its attacks on late-stage nests no laying opportunity is wasted. Hence, as with parasitic egg laying, ‘farming’ behaviour requires that the parasite can assess the host's reproductive stage and acts accordingly by destroying late-stage nests.