Diseased Bird: sick Cassin’s Finch

There have been a LOT of Cassin’s Finches this Spring and I have been noticing several stressed or sick individuals. They show stress by a general lethargic, apathetic demeanor, puffed feathers and solitary behavior. I have not observed any swelling around the eyes or tumors. I have observed them eating. I am seeing perhaps two sick birds a day.