CULTURALLY CORRECT SONG DIALECTS ARE CORRELATED WITH MALE AGE AND FEMALE SONG PREFERENCES IN WILD POPULATIONS OF BROWN-HEADED COWBIRDS

Variation in vocal behavior among local populations of songbirds may b e significant to females in mate choice. In a study of dialect populat ions of brown-headed cowbirds, estradiol-implanted females from two di alects held the pre-copulatory lordosis posture longer in response to playback of the local flight whistle song than to foreign whistle type s from adjacent and more distant dialects. Females were held in captiv ity for a relatively brief period prior to testing and received no tut oring so discrimination was based solely on experience in the wild. Th is is the first study to show evidence of discrimination by female cow birds based on flight whistle type. Evidence is presented from one of the study dialects that the majority of yearling male cowbirds are voc ally distinct from resident adults in having either foreign or incompl ete local whistles. Although these yearlings are fully mature sexually , they have little or no mating success. The correlation between femal e whistle preference and male mating success suggests that the ability to give the correct local whistle type may be a characteristic used b y females to assess age and quality of a potential mate. A learned fem ale preference for the predominant local song type may be a factor in the stability of these dialects by making it adaptive for males to con form to the local dialect.