Communication in prairie grouse: II. Ethological isolating mechanisms

Abstract

Ethological isolating mechanisms, including interspecific communication, are often critical in maintaining species integrity among closely related, sympatric, avian species. Greater prairie chickens and sharp-tailed grouse hybridize within a narrow area of sympatry in central United States. This study investigates the reactions of males and females to conspecific and heterospecific stimuli. Males of both species courted live heterospecific hens less than conspecific females on mixed display grounds. Sharptail males, however, showed greater discrimination of live females and taxidermist mounts of hens in the copulatory position compared to prairie chicken males. Males of both species maintained mutually exclusive territories on mixed grounds through similar aggressive displays. Prairie chicken males responded significantly to playbacks of sharptail coos, cork notes, composite sounds, and gobbles. Sharptail males reacted to prairie chicken cackles and booms. All of these vocalizations except composite sounds have aggressive intraspecific functions. Females showed very strong preferences for conspecific males on naturally occurring mixed display grounds and in captivity. Although F1 hybrid hens initially preferred prairie chicken territories in captivity, most hybrid and backcross hens mated with sharptail males. Strong preferences by prairie chickens and sharptail females is expected due to highly developed polygyny and relatively low paternal investment in clutches and broods. Of the possible isolating mechanisms between these species, interspecific communication appears to predominate in areas of sympatry.