GREENSBORO, N.C. — Biologists have noticed a concerning number of goldfinches and pine siskins are dying in North Carolina.

According to a release from the North Carolina Wildlife Resources Commission, experts believe the birds that have turned up dead in several yards across the state over the past month were infected with salmonella.

These experts say feeders could be the culprit for exposing these birds to this deadly infection. Salmonella is typically transmitted through food or water contaminated with feces. That is why bird lovers, like Barbara Haralson, are making sure all her bird feeders are clean.

“They are just in such close proximity all the time that it's very easy for them to spread diseases from one another. So they’re not just clustered at bird feeders, they also cluster when they roost together at night. They’re clustered together just as they forage around for food together," Haralson says.

Birds infected with the disease may appear thin, fluffed up, depressed, have swollen eyelids, or may have trouble passing waste.

If you have a bird feeder, biologists are recommending cleaning it frequently with diluted bleach solution, no more than 1-part bleach to 9-parts water.

The North Carolina Wildlife Resources Commission urges residents to report any suspected salmonella cases to the wildlife helpline at 1-866-318-2401.