What is this?

[dlavalleur]

Has anyone ever seen this on your chickens?

I thought at first she was molting but this has been going on for 3 months now.

 

[Crazy for Chickens!]

Do you have a rooster? Looks like she is being over bred.

 

[azygous]

There may be a combination of factors in play. Yes, I've had something similar show up from time to time in my flock.

One factor is an external assault on the feather covering, either from a predator or from over-mating or from chronic picking from fellow chickens.

Another factor is molt.

And the least understood or considered factor is genetics that hinder feather replacement.

This last one has occurred in my flock recently. Once last year with a Cream Legbar hen who skipped her first adult molt and went all winter with a threadbare suit of feathers, and finally molted in early summer. The second one is occurring now with the female offspring of that Cream Legbar who survived a hawk attack, losing all her back feathers, and still sports a bare back six months later. And she hasn't showed any signs she will have her first adult molt anytime soon.

Another thing that could be causing this feather loss is mites. I see some red, irritated skin which may indicate parasites of a blood sucking nature. I would inspect the chickens and coop after dark to be sure this is something you can rule out.