[violet]

A couple of our hens are moulting and so have sort of random feather loss, but a couple of them have bald patches around their necks, one mainlly around the back of her neck and the other under her neck at the front...do I presume that their is some aggressive behaviour here? neither of them have broken skin and I have not seen the pecking...unless they do it after lock up!

[Bodger]

When new feathers start to come through, they are full of blood and chickens sometimes take a liking to it.
I'd also give them a quick dusting of something incase some depluming mite are at work. On the other hand, it might be just an ordinary moult.