DECEPTION BY HELPERS IN COOPERATIVELY BREEDING WHITE-WINGED CHOUGHS AND ITS EXPERIMENTAL MANIPULATION

White-winged choughs (Corcorax melanorhamphos) are obligate cooperativ e breeders, living in groups which may contain up to 20 birds. Althoug h breeding is dominated by a single pair, all birds contribute to rear ing young, including the provisioning of nestlings. However, some bird s which have carried food to the nest, even to the point of placing th e food in the gaping mouth of a nestling, consume the food themselves rather than provision the nestlings. Birds which fail to feed nestling s are typically young, and are only likely to fail to deliver food whe n they cannot be observed by other group members. Birds which have jus t failed to deliver food are more likely to engage in alternative help ing behaviours such as allopreening the nestlings than are helpers whi ch have just delivered food in the conventional manner. Failure to del iver food is almost eliminated when foraging constraints are experimen tally reduced by supplemental feeding of the group. Collectively these observations suggest that young white-winged choughs act deceptively by simulating helping behaviours without sacrificing food supplies.