What's going on here with this chicken's rear end?

[Millerhenhouse]

This chicken--and a couple of our other ones look like this. (see pic). Namely, it's two RIRs and a silver-laced wyandotte. I had only noticed the rear end of the chicken shown here, but now that I looked at them while they're on their roost, more than just this one looks like this.

Is this something that should be concerning to me?

They've also got bare backs that is from pecking from the others. We're doing the pine tar, but it's not doing much good. No one's very bloody at all--it's really just bare, pink backs. And now there's this. What's going on? Suggestions? Recommendations?

Thanks!

 

[GoldenSparrow]

I would like to know as well?

 

[Firearia]

I had a couple chickens like this during summer. The other chickens were pulling out the feathers from their fluffy butts. Eventually the feathers grew back. :3