Papilloma viruses in chaffinches give rise to warty growths - which have colloquially been called "tassel foot", and I think you would agree, looking at the photographs which have been kindly sent to me by David White, it is a very good descriptor.

Papilloma viruses in humans cause skin warts, which are very common but usually resolve spontaneously. In fact, I remember as a child, my Dad 'buying my warts from me' for a 5p (or maybe it was a sixpence?) - and magically they used to vanish! I think he just got his timing about right. More...