Testosterone-dependency of male solo song in a duetting songbird - Evidence from females

► Steroid-hormone sensitivity of solo song in a tropical duetting songbird was investigated. ► Solo singing of dominant males was associated with elevated testosterone levels. ► Testosterone-treatment induces male-typical solo singing in females. ► Confirms that solo song can be activated by gonadal steroid hormones. ► Suggests complex relationship between song behaviour and testosterone levels in tropical birds.