I am stumped and hope y'all can help. We have a parrot finch that's been with us for about a year and has always seemed quite healthy. Over the past couple of weeks, he has developed some very strange symptoms that I've never seen. He seems to have no balance; has trouble perching and when he tries to fly, his wings are really uncoordinated, going ever which way. His legs also seem to fail him--one in particularly splays when he's moving around on the ground. At first we thought he'd broken a wing, then a leg, but both seem structurally okay. He *can* perch if he's still, but when he starts moving it's as if he's lost all coordination.
He was spending most of his time on the aviary floor so after observing for a few days and a good visual exam, we've removed him to a small hospital cage. He seems comfortable on a low perch and is eating & drinking just fine.
Having done some reading the closest thing I can find to this set of symptoms is West Nile virus.

Although we have seen a couple of mosquitoes already, we've not yet opened up the aviary (enclosed in plastic for the winter), so that seems like a long shot.
Any ideas?
TIA,
Pat