Birds

Mimicry

Mimicry, a basic form of deception, is apparent in 15 to 20 percent of avian species. In almost all cases, the mimicry is vocal—birds are known to reproduce the sounds made by other avian species, other animals, and even human-made objects. Well-known mimics include parrots (Psittaciformes), the northern mockingbird (Mimus polyglottos), and drongos (Dicruridae). While no single function has been determined for such accurate vocal mimicry, some species, namely within the drongo family, appear to deceptively use this ability. Birds have been known to mimic calls of other bird species in order to attract individuals of that species to assist in mobbing a predator or to aid in foraging. It is argued that birds that produce accurate mimetic vocalizations in appropriate contexts are acting deceptively because the calls affect others in ways that benefit the caller. Alternatively, if birds randomly produce the calls, regardless of context, they are not behaving [Page 80]deceptively, even if their calls occasionally impact the behaviors of others in a way that benefits the caller. The context of mimetic calls must therefore be studied to determine if they are a true example of deception.

Reproductive-Related Deceptions

Related to mimicry is brood or social parasitism, most common in the cuckoo (Cuculidae), cowbird (Icteridae), and honeyguide (Indicatoridae) families. Brood parasitism is a reproductive strategy in which individuals of one species (the parasites) lay their eggs in the nests of another species (the hosts), leaving the host to raise the parasitic young. It is a prime example of coevolution because the hosts gradually evolve strategies to detect parasites while parasitic eggs evolve to look increasingly similar to eggs of the host, limiting the number rejected. The young of some species even mimic the begging calls or plumage of the hosts' young. If the parasites are not detected, the young of the hosts are typically killed. Nestlings of certain parasitic species have concave backs to push host young from the nest and specialized bill hooks to kill them, or they simply outcompete them by eating all the food that the adult hosts provide. In other parasite species, the adult will eject the eggs of the host as it is laying its own. Brood parasitism severely impacts the reproductive success of the host while benefiting the parasite.

Another form of deception that impacts reproductive success, extra-pair mating, has been reported in at least one species in nearly every avian family. The term applies only to bird species that pair bond, and has been well studied in the pied flycatcher (Ficedula hypoleuca) and great reed warbler (Acrocephalus arundinaceus). Extra-pair copulations occur when an individual mates with another who is not its social pair. Males have been known to mate with a first female and attempt to attract a second after she has laid her eggs. Some species, such as the pied flycatcher, achieve their deceptive polygyny by defending multiple territories, known as polyterritoriality. After its mate lays eggs, the male will establish a second territory from which to call. Species such as the great reed warbler, on the other hand, defend large territories, and will call to attract a secondary female from a location far away from their mate. Whatever the method, extra-pair copulations can be called deceptive only if researchers are able to ascertain that the secondary female is not aware of the male's mated status. Extra-pair mating has been shown to reduce the breeding success of the secondary females that are left to raise the young alone while benefiting the male by increasing his fitness.

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