The genetic sex is determined by the chromosomes. The gonosomes (= sex determining chromosomes) of a male chickens are ZZ and those of a female chickens are ZW, as opposed to mammals, where the males are characterized by XY chromosomes and females are equipped with XX chromosomes.
The phenotypicSet of observable characteristics or traits of an organism. The term covers the organism's morpholog... sex is determined by the gonads (testicles/ovary) and secondary traits.