In May reports of mostly young fledgling birds stricken with a mysterious illness began trickling into state Departments of Conservation and wildlife rehabilitators started seeing sick birds with unusual symptoms.
The symptoms were a combination of a conjunctivitis-like crusting of the eyes rendering birds blind and neurological behaviors, such as shaking, inability to stand, disorientation and extreme lethargy. Rehabilitators tried a variety of treatments with little success.
The first reports were centered around the Washington, D.C., region, but by June quickly widened to include Maryland, West Virginia, Virginia, Delaware, New Jersey, Ohio, Tennessee, Florida, Indiana, Pennsylvania and Kentucky.
A few scattered reports of birds with similar symptoms were reported in other states, but not in any real concentration.
The disease seemed to primarily strike songbirds. Birds most commonly affected include the American Robin, Blue Jay, Common Grackle, European Starling, and also Northern Flicker, Northern Cardinal, House Finch, House Sparrow, Eastern Bluebird, Red-bellied Woodpecker, and Carolina Wren. Most affected birds were juveniles, just out of the nest and still being fed by their parents. Symptoms were also reported in much smaller numbers in other woodpeckers and even a few hawks, which may have fed on afflicted birds.
Several theories pointed to the massive 17-year Brood X cicada hatch since the illness coincided with the regions and timing of the emergence of that brood. Meanwhile, veterinary labs were attempting to identify the causative agent. They have ruled out a number of possibilities, including salmonella, chlamydia, avian influenza, West Nile virus, various herpes viruses and other diseases. They also ruled out mycoplasma, a bacterial infection that attacks House Finches, causing a conjunctivitis-like swelling and crusting, and often leading to blindness. They have so far been unable to find anything that would cause contagion.
Erring on the side of caution, advice to take down feeders and remove bird baths was given across most of the Eastern United States, even in states where no illness had been reported. The theory given was that the disease was potentially being spread at feeders and baths where birds congregate. As the bulk of reports were coming from people with backyard feeders, that seemed a link to the illness.
Though the cicada theory received pushback due to some illnesses occurring outside the Brood X range, the speculation kept circling back to the common element, insects. Regardless of the foods a bird eats as an adult, almost all songbirds are fed a steady diet of insects while they are in the nest. They require enormous amounts of protein to grow to adult size within a few weeks.
The most impacted birds were larger juveniles who would have been fed larger insects, like the easily available cicadas. And while Blue Jays, Starlings and Grackles certainly do congregate at feeders as adults, their fledglings don’t until their parents stop feeding them. American Robins consume fruit and insects and do not come to feeders at all, though they frequent bird baths.
The illness began to show signs of abating in July and in late July the Cornell Lab of Ornithology and the Cornell College of Veterinary Medicine issued a joint statement associating the disease with the Brood X hatch and saying removal of feeders and baths was no longer a needed precaution. The abatement of the illness pointed away from a contagious illness, which should have continued to spread as birds, finished with breeding, began to migrate.
The Cornell Wildlife Health Lab, housed in the Cornell University College of Veterinary Medicine, has monitored the situation and stayed in close contact with other agencies and labs. They noted that though the disease had caused the deaths of many of the first hatch of young in the affected areas, many birds were able to have a successful second nest.
Though New York and the New England states were spared from this outbreak, labs and agencies will continue to monitor cicada hatches in coming years to see if there is a link to another brood and do testing to discover what caused the outbreak.
So feeders can go back out, but with common sense precautions. Feeders and baths must be cleaned regularly. Moldy seed can spread a deadly disease called aspergillosis, which affects the birds’ respiratory systems, so clean out feeders and rake up seed on the ground – which also eliminates rodent attraction. If you have House Finches at your feeders, tube feeders can spread the conjunctivitis that blinds them and causes a lingering death. Platform feeders have the least likelihood of cross contagion.
Cleaning means a one-to-nine parts bleach solution or hot soapy water and a strong brush. Planting native plants that will both attract insects and bear seed or fruit is a good way to safely supplement feeder offerings. Thankfully, we can now resume supplying our feathered friends with food and water without worry of being the cause of illness or death.