Interspecific Preening Invitation Display of Parasitic Cowbirds

Abstract

Brown-headed Cowbirds (Molothrus ater) solicit heteropreening from individuals of other species of birds by giving a special head-bowed display. Through persistent presentation of the display, heteropreening may be induced from a variety of species, including Red-winged Blackbirds and other forms that do not engage in intraspecific grooming. Intraspecific presentation of the display is uncommon among cowbirds and does not result in heteropreening. The readiness of captive cowbirds to display is increased by depriving them of close contact with individuals of other species. There is no marked seasonal variation in frequency with which the display is given, and bilateral castration does not affect the readiness of males to display. Tests with live birds and dummies suggest that cowbirds will not display to species larger than a Mourning Dove and are reluctant to display to black plumaged birds. A similar display was seen in captive Red-eyed Cowbirds (Tangavius aeneus). Avian appeasement displays are discussed, and it is suggested that interspecific display of parasitic cowbirds is an adaptation for parasitism functioning to descrease the probability of attack by individuals of host species by decreasing their aggressive tendencies. || ABSTRACT AUTHORS: Author