http://www.baroquewallpaper.com/archives/1105
How do Chickens become prganant. What determines a rooster form a Chicken at Birth.?
Birds do not technically ‘become pregnant’ in the way we humans do, since they reproduce by laying eggs. A female bird that’s carrying eggs that haven’t been laid yet is referred to as gravid, not pregnant.
Like most birds, chickens do not have a penis. They mate simply by pressing their cloacas together in what is known as a ‘cloacal kiss’ (the cloaca is the single opening birds use to excrete, mate and lay eggs, in case you didn’t know). To do this, the male stands on top of or over the female and tucks his rump beneath hers to bring their cloacas together (some species mate in flight, but this is how most do it). His sperm is then squirted from his cloaca into hers, and swims up her oviduct to her eggs, fertilising them. The eggs are then coated in shell and laid, and will hatch after an incubation period.
In the few birds that do have a penis, such as ducks and ostriches, it is out of sight inside the cloaca until mating is about to occur. It then emerges and is inserted into the female’s cloaca, delivering sperm inside her. What follows is the same as for other birds.
I’m a little confused by your question: “What determines a rooster from a chicken at birth?” – a rooster IS a chicken. Rooster or cockerel is the name for a male chicken. A female is called a hen.
Painting Rooster with Chicken Feather Brush by Datong Xu
[affmage source="ebay" results="100"]Rooster Chicken[/affmage]