neck-ed as a jay bird

Historically, in the Ozarks, one was not nude or naked, but, rather, "neck-ed as a jay bird". Why a jay bird, since no birds wear clothes?

I know birds molt and I have seen some nearly naked chickens. And, with no feathers on their heads, turkeys and vultures are more naked than jay birds.

So, how did jay birds become the standard for comparison to nakedness?

Emmett