Missing Feathers around neck - What is wrong?

[teach28]

I have three chickens and one of them has feathers missing around her neck. This had happened in the past with a smaller patch, but they grew back so did not worry. Now today I noticed she is really bald around her neck and don't know why.

Any advice would be great!
She is about a year old and we have raised her since the incubator.

Here are some pictures of her with her missing neck feathers:

 

[Granny Hatchet]

is she with a rooster?

 

[teach28]

No - we only kept the roosters until they were about 4 months old and then found them a new home. Just 3 hens now.

 

[Granny Hatchet]

a hen could be pecking her but i would check for mites i guess

 

[JadedPhoenix]

is she with a rooster?

That's my thoughts as well. A roo can be a little rough on some hens.

 

[Granny Hatchet]

sometimes if there is no roo the hen will step up and act like one to an extent.......

 

[teach28]

Odd thing is that this is the one who will take a stand against our dog and seems would take on this role of acting like a roo, not the other two.
Thank you for the feedback!

Is there a way to deter whichever hen is picking on her to stop without separating them?

 

[Granny Hatchet]

if she is head hen maybe something in the coop caught the feathers or the dog itself? look for them where she stays. the feathers i meant.