As far as i know, this happens to all parakeets, not just females. The stripes disappear because your parakeet is getting older. It's kind of like when a fawn looses the whites spots on his back. It's perfectly normal and there is no problem. :)
Only the males change color. If yours is mature it must be a female.
The only 2 reasons your parrot loses feathers is by molting or if it's in distress. Some birds may experience severe molting, but it is uncommon. If the parrot is in distress it can be for a variety of reasons that she is plucking. See an avian vet for solutions or visit an avian specialty store for over the counter products that may help.
The male buzzard has separated feathers at the end of their wings. These look like fingers. The female buzzard does not have these extra feathers.
The female of the species has an orifice at the section of the back that connects to the tail feathers. If you pull the feathers aside with a fingertip you can see the actual vagina like orifice.
the female parakets have lighter feathers and the males have dark feathers
Your parakeets may have not been male and female they might have just been 2 females or 2 males.
I guess its refers to the Mallard...
Well, if parakeets are healthy and happy both male and female will chirp alot. That being said, male and female parakeets will often screech if they are not happy or if something like your music being played too loud or a cat is bothering them.
both male and female
By there noses. A males nose is blue. A female is pink or a light peach
I don't think so. I read that adult female parakeets noses are brown and that adult male parakeets noses are blue. But, young female parakeet's noses are "bluish" and a young male parakeet's nose is pink.
that's normal