Induction of Singing in Female Canaries by Injections of Male Hormone. ∗

Abstract

It is generally recognized that singing in canaries is limited to the male and as such this may be considered as a secondary sexual characteristic. In order to determine if this behavior is conditioned by secretions of the testis, male hormone was injected into female birds.

The canaries used were raised by a local breeder, Mr. J. Frederichs, who has developed a hardy strain of birds by acclimating them to life out of doors throughout the year. They were brought into the laboratory in January, a few weeks before the normal breeding season. Females can be distinguished from males during the breeding season by observing differences in the cloacal eminence. The male cloacal eminence is long, pointed and projects ventrally while that of the female is broad and is directed posteriorly. At no time did the females sing previous to injections; they gave only the characteristic “chirp” of the female and were busy carrying bits of straw and paper, to build nests.

Testosterone propionate (Oreton)† in 0.2 cc doses equal to 5 mg of hormone, was injected into the breast muscles every 3 or 4 days until singing occurred. Five birds were used in this study.

In 4 out of 5 birds, the typical male song was sung by the injected females. One of them began singing after 2 injections, the others after 4 injections. The singing was continued for periods of 5 to 13 days after the last injection, depending on how much hormone was given. The remaining bird, though it sang no sustained song, behaved like the normal males or the stimulated females in her attempts to sing. She strutted on her perch, swelled out her throat and moved it as if singing but the sounds emitted were interrupted and resembled only portions of the male song in variation and duration.