House Finches may become infected with a bacterial eye disease, avian conjunctivitis, that causes red, swollen, runny, or crusty eyes. Purple Finches, Goldfinches, and other birds may become infected as well.
In extreme cases the eyes become swollen shut and the bird becomes blind. You might observe an infected bird sitting quietly in your yard, clumsily scratching an eye against its foot or a perch. Birds will often sit fluffed up as their energy reserves diminish. While some infected birds recover, most die from starvation, exposure, or predation.
Avian conjunctivitis easily spreads at bird feeders. When a sick bird finds a feeder, it may be reluctant to leave that food source because it cannot see. Healthy birds pick up the infection and spread it to other feeders.
You can help reduce the spread of the disease by following this routine to disinfect your bird feeders:
Also consider removing your bird feeders this time of year, when the food birds need is naturally abundant.