What is 'normal' feather loss and what is not?

[clairabean]

A few of my banties have quite bald chest/bellies. I thought it may be due to broodiness. Do they pluck their own feathers when making a nest? So I checked all my chickens for baldness. Two are quite bald under their chests, one is quite bald under her tail area- above and below her vent.

Is this normal? Any ideas or thoughts?

It is -18*C during the day. Should I wait for it to warm up or try to snap them out of broodiness now?

 

[scbatz33]

broodies will develop bald patched on their chest, however loss of feathers around tail and vent makes me think lice or mites.