TESTOSTERONE INDUCTION OF MALE-LIKE VOCALIZATIONS IN FEMALE BUDGERIGARS (MELOPSITTACUS-UNDULATUS)

Budgerigars possess a complex learned vocal repertoire that includes a long rambling song called warble. While both males and females can wa rble, there are marked sex differences in the amount of song produced. Males generally warble daily at a high rate, while females rarely sin g. Both the quantity and the quality of male warble are influenced by circulating levels of testosterone. Males have higher circulating leve ls of testosterone than females. In this study we asked whether admini stering testosterone to adult female budgerigars would activate male-l ike vocal behavior. Four females were implanted with 8-mm Silastic imp lants filled with testosterone and recorded before and after implantat ion. Within 10-14 days, all four birds showed: (1) changes in cere col or to the male-like condition (blue), (2) male-typical patterns of pre copulatory behavior, and (3) an increase in their rate of warbling to male-like levels. Sound analysis revealed that the acoustic structure of the testosterone-induced female warble is similar to the male warbl e. These data indicate that sex differences in budgerigar vocal behavi or are not based on early organizational effects of steroid hormones, but rather are probably the result of adult sex differences in circula ting testosterone levels. (C) 1996 Academic Press, Inc.