Pennsylvanians can feed birds again.
A disease that appeared from spring into summer blinding and killing a variety of songbirds in at least 10 states left wildlife experts and officials stumped as to its cause, and recommending people stop filling feeders in the belief it could mitigate the spread of the illness where birds congregated.
Now, the disease has apparently run its course, leaving experts without knowing if it will reappear.
Martin Hackett, a spokesperson for Penn’s School of Veterinary Medicine, said the school’s Wildlife Futures Program, which hosted an online reporting form, originally saw high numbers of reported bird deaths in the spring. But the numbers started dropping by late July into August.
Tests ruled out avian influenza and other viral and bacterial diseases. No poison, toxin, or parasite was identified as a possible cause. Hackett said the cause of the illness remains unknown.
The disease struck birds in Pennsylvania, Delaware, Tennessee, Kentucky, Virginia, West Virginia, Maryland, Indiana, Ohio, Florida, and elsewhere. It killed a range of species, all suffering ocular and neurological issues, marked by swollen eyes with a crusty discharge, and erratic flight and stumbling.
Species affected included blue jay, European starling, common grackle, American robin, Northern cardinal, house finch, house sparrow, Eastern bluebird, red-bellied woodpecker, Carolina chickadee, and Carolina wren. The malady appeared to affect juvenile birds more than adults.
There was some speculation that Brood X cicadas that emerged this spring after 17 years could be linked to the disease. But officials said deaths were occurring in areas where the brood wasn’t particularly active.
The USGS National Wildlife Health Center, the University of Georgia Southeastern Cooperative Wildlife Disease Study, the University of Pennsylvania Wildlife Futures Program, and the Indiana Animal Disease Diagnostic Laboratory were all part of the investigative team, as well as various state labs. None had luck finding a cause.
Recently, the Pennsylvania Game Commission lifted its recommendation to stop feeding birds, but it still recommends feeders be cleaned weekly with soap and water, then disinfected with a 10% household bleach solution before allowing to dry well, and refilling.
The Game Commission said that a lot is “still unknown” about the disease, first documented in the Washington, D.C., area in May. There is no indication feeding birds was a contributor, but the commission still recommends caution as “the issue appears to be resolving on its own.”
On Tuesday, the Delaware Department of Natural Resources and Environmental Control also lifted its advisory against bird feeders and baths.