Sentence:  I ſhall call this bird the painted vulture. ... the head and neck bare of feathers nearly down to the ſtomach, when the feathers begin to cover the ſkin, and ſoon become long and of a ſoft texture, forming a <WSD>ruff</WSD> or tippet, in which the bird by contracting his neck can hide that as well as his head: ... 
Meaning of the word marked with <WSD> tags:  A set of lengthened or otherwise modified feathers on or around the neck of a bird.