Chicken with weird lump on back, feather loss - pictures

[lorelei14]

I have two Rhode Island Red cross birds, both female & about 2 years old. One of the hens has a weird red lump towards her tail, about 1.5cm in length & 5mm in diameter. It is like a round nodule, & around this area her feathers are lacking fluff near the base where the feather meets the skin. She also has bare red patches near her vent, & on her chest. She is otherwise perfectly healthy, eating & drinking as normal (& chasing pigeons..) The other hen is unaffected. I have recently treated the coop with a disinfectant, rubbed red mite powder into her patchy areas and treated the bedding with a mite powder. These are the first chickens i have owned, & live in a city where it is difficult to find people who can advise! Her egg production is normal, they have slowed a little from one egg a day, but generally at the very least they both lay one egg every two days. I had noticed some small red dots on the eggs, which is why I treated them for red mites, but after a few week's application of powder there doesn't seem to be any change The other hen is completely fine & unaffected.

I have included a couple of pictures, apologies for the blurry quality, they don't like standing still! Any advice would be much appreciated, as worried it could be an underlying problem.
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[Rocky Top Chick]

It's normal, it is their oil gland. They use this gland when preening.

 

[sunket77]

that looks to be her oil gland, It is just before the tail. I would be 100% certain that's what it is. All chickens have them, if you look and pull the feathers back on you other chickens you should be able to see theirs also. Some are more pronounced than others. They rub their head there and spread oil around for protecting their feathers. I think sometimes they can get infected or blocked but not positive on that (maybe someone else on here would know more about blockage) but it looks pretty normal from the pics. Your other chicken might be pecking at her and causing the feather loss for some reason I have found RIR are pretty bad about pecking, out of all the breeds I have the red ones are the worst about it. Try some rooster booster which should stop her from doing it. OR could she be molting? have you had them since chicks? the reason I ask is molting can be kinda scary if you have never seen it before, feathers everywhere and naked chickens!

 

[horsetails16]

I just found this on one of my chickens, she was preening and kept raising her back feathers and rubbing her beak on this lump. I thought something was wrong, I investigated online and this is exactly what it is (thank goodness!!)