Chickens biting at nub on upper back

[notv]

I've noticed one of my chickens really biting onto a little nub/nipple looking thing on her upper back, it's not in or near her vent, but above it.

Then, I noticed another hen doing the same maneuver. Never noticed this before last week (had them almost a year now).

What is this nubby thing? Is there a purpose for it -- is this where they secrete the fluid for their feathers? Should I be concerned about this behavior?

Many thanks!
Steve

 

[Mac in Wisco]

That's their oil gland or "preen gland" they take oil from it and apply it to their feathers.

 

[notv]

aha! many thanks for the insight.

 

[canada-goose]

I used to be worried about the "wart" on my chickens' backs too.....until I read about oil glands! I was young and foolish back then.

 

[Chickadoodoo]

i saw that on my chicken too and i was worried glad i know what it is!