Inability of Testicular Hormone to Masculinize Plumage and Eye-Color of Female Brewer's Blackbird.

Abstract

Attention has recently been called to a relation between testicular hormones and some secondary sexual or “ambosexual” characters in several avian species, but it is still too early to say how widespread the observed reactions may be. In the English sparrow, Keck1 has found the color of the beak an excellent indicator of the amount of testicular hormone circulating in the blood, while the plumage is not such an indicator; van Ooordt and Junge2 find that in one of the gulls a testicular hormone is necessary for development in the male of colors in bill and feet which are found in both sexes during the breeding season; and Gallagher, Domm and Koch3 report that injection of purified testicular extract restores the plumage of Sebright capons to its normal form and color. In light of these findings, and since plumage and eye-color of the male blackbird (Euphagus cyanocephalus) seem to be unaffected by the injection of theelin,4 it was thought desirable to see if secondary sexual characters in the females of th...