I took the attached pic of a Jay on 19th April at the Stover Country Park in Devon. It clearly has some sort of white canker on it's feet - is this a form of Trichomoniasis on this species. There is a post dated 04/03/15 on this site which also shows a Jay with a similar problem, but no conclusion seems to have been made as to what it was.
Hi Chris, Trichomoniasis is a parasite that lives in the back of the throat/gullet area of a bird and mainly affects finches although other birds can get this too. Your Jay does not have Trichomonosis but they do sometimes get other forms of Fringilla papillomavirus (which specifically affects finches) - my best guess (but I'm no expert) is that your Jay may have something like scaly leg mites that can burrow and cause lesions on the feet "Cnemidocoptes pilae"
I will go with the papillomavirus its not nice to look at and I don't take pictures of any bird with this infection because I feel for the bird and there is nothing we can do for it the only thing I know of is to keep all your feeder clean so not to spread it on to others :(
One of the Jackdaws at the rear of the college has 'warty feet' but they are much worse than those of the Jay in your pic. Maybe it's a Corvid variation of the Finch disease? I don't know how long they survive with this condition but the Jackdaw in question has had this ailment for more than a year.