Egg Laying Bird with Male Plumage Demonstrates the Puzzling Nature of Sexual Differentiation and Selective Mate Preferences in Zebra Finches

Zebra finches (Taeniopygia guttata) are oscine Passerine songbirds that are native to Australia. Zebra finches have sexually dimorphic plumage, song nuclei, and behavior. The role of chromosomes, hormones, and genes on sexual differentiation are not completely understood. A gynandromorph in our aviary had male plumage, a male partner, and produced viable offspring. Mate preference tests revealed lower preference for the gynandromorph and its progeny than controls, suggesting that they had some traits that made them unattractive to other birds. Gynandromorph lineage males had greater same-sex preferences than control males. Chromosomes in birds are different than those in humans. Males are homozygous ZZ, and females are heterozygous ZW. All sampled gynandromorph tissues, including those in sexually dimorphic plumage regions, had ZW female chromosomes. Of zebra finches, males sing and females do not. Because of this, the regions associated with song learning and production, collectively called a song system, are larger in males than in females. We thought to measure the size of the song nuclei in our gynandromorph and compare it to control males and control females. For song system comparison of the gynandromorph, volume, cell number, and cell size of sexually dimorphic song nuclei were measured. The volumes of the song nuclei for the gynandromorph were consistently between the song nuclei volumes of males and females. Additionally, because birds can see in the ultraviolet spectrum of light, color spectra were analyzed to determine if the gynandromorph or its progeny had plumage differences that were undetectable by the human eye. Video analysis of the gynandromorph and its mate is being completed to determine if the gynandromorph sang and to observe nesting behaviors