I quote from an article published in the Spring 1997 issue of Crossing Paths,
published by the Washington Dept. of Fish & Wildlife for their Backyard
Wildlife Sanctuary Program, titled "What's Wrong With That Bird?"

"The most common diseases of birds that visit feeders are avian pox,
salmonellosis, trichomoniasis, and aspergillosis. There are others, but
these are the ones most often noticed.
Avian pox is the most noticeable disease, and probably the one that generates
the most questions. You will notice wartlike growths on featherless surfaces
of the bird's face, legs and feet, and sometimes the wings. Sometimes warts
close to the bird's eyes make it appear to have bulging eyes.
Avian pox is caused by a virus, similar to the virus that causes warts on
people. It does not necessarily kill the birds outright, but it can
interfere with their daily lives enough to kill them indirectly. The growths
can become large enough to impair vision or eating ability. The growths on
toes can affect perching, standing and walking ability. With these
debilitations, birds are more vulnerable to predation, dehydration,
starvation and weather. The growths can also develop into sores and become
infected.
The virus is spread by direct contact with infected birds, by picking up shed
viral cells on food or feeders, or by insects carrying the virus onto the
bird's body. People and pets cannot contract avian pox, but always wear
gloves when handling diseased wildlife anyway."
The article emphasizes prevention or minimization of the spread of disease by
avoiding overcrowding (spreading feeders around your property); cleaning up
discarded seed; cleaning and disinfecting feeders regularly - daily in a
disease outbreak; store fresh seed in airtight containers; and eliminate all
sharp points and edges on feeders.
I haven't noticed any house finches with avian pox this year but I've seen
finches with it in the past. Of more concern were the pine siskins who were
dropping dead at our place in Pt. Angeles from salmonellosis the summer of
1995- hopefully that outbreak is over.
Patti Gotz/Seattle
redquilter at aol.com