Fertilization in commercial chickens is usually the result of natural mating. However, in some cases, artificial insemination is commonly practiced. The turkey industry especially depends on artificial insemination since natural mating is virtually impossible as a result of intense genetic selection for conformation and body weight. The completed mating in chickens is the culmination of a sequence of behaviors. The rooster will initiate mating by exhibiting courtship behavior: dropping one wing ...and dancing in a circle (the lowered wing will be on the inside of the circle dance). The hen will crouch (dip her head and body) to indicate receptiveness to the male. The rooster will then mount the hen and grab her comb, neck feathers, or the skin on the back of her head or neck to help hold onto the hen’s back. The next behavior is the tread (the rooster walks quickly in place on the hen’s back) and finally, the completed mating of the behavioral sequence. The completed mating occurs when the rooster dips his tail to the side of the hen’s tail and spreads his tail feathers so that their cloacae come into contact. At this point the rooster’s ejaculate is released directly into the hen’s vagina via her cloaca. In the typical breeder house with thousands of birds, the entire sequence of behaviors do not always occur, and the courtship dance is frequently left out of the sequence. Chickens are polygynous, but certain males and females selectively mate regularly. Some females in the flock will show avoidance to specific males, and therefore are rarely mated by those males.