Hen is changing sex

[greenfamilyfarms]

Like others have said, some hens grow spurs. Just like how some human women can have male sex characteristics, such as facial hair and chest hair.

 

[mstrrlm]

I suspect hens that are closer to the origins of wild chickens such as the Jungle Fowl where the hens had to defend their babies from predators more often would still grow spurs.

 

[Lothiriel]

I had a Black Australorp hen who grew spurs -- I think she was about 3 years old when they came in. They grew to about 1 inch long, and she wasn't the dominant hen either and I had no roosters. You don't need to worry about your girl.