The Wild Side: What?s behind bird die-offs?
On New Year’s Day, 2011, thousands of birds rained from the sky in the small town of Beebe, Ark., in a phenomenon that became known as the “aflockalypse.”
Samples of the dead birds were collected, and the cause of death was apparently trauma-related. It was thought the birds were startled from their roost in the middle of the night by celebratory fireworks. The birds were apparently frightened and disoriented, causing them to crash into each other, buildings, trees and the ground. Some had burst lungs and hearts, literally scared to death by the disturbance. The same thing happened again in 2012; however, due to a fireworks ban in the city, there were far fewer bird deaths. I was all set to write about this aflockalypse this past New Year’s, but no deaths were reported.
Mass die-offs of birds are not uncommon. In fact, ornithologists (bird scientists) I have spoken to tell me that birds die by the thousands every year. Sometimes it is natural causes, like disease, exposure to weather extremes or starvation. Other times it is related to human activity; for example, flying into windows, wind turbines, structure support wires or fireworks. Natural die-offs tend to happen in areas of low human population. For example, many migratory songbirds fly over the Gulf of Mexico. I would expect there are birds that die of disease, exhaustion, or starvation traversing a thousand miles of ocean.
When I came into the office Monday morning, I received a phone call from a concerned homeowner who found several dead birds around their birdfeeder and near the house. Most of them appeared to be common redpolls. Unfortunately, I knew right away what had happened. Redpolls are one of our most susceptible bird species to a bacterial infection called Salmonella. Our wildlife health division has received scattered reports of small numbers of sick and dead birds at backyard feeders around the state. Pine siskins, redpolls and goldfinches were all documented with the fatal infection in Dane and Washington counties. To date, they have a total of 18 counties reporting bird deaths, including Price and Oneida counties. That day, I received five reports of dead birds from homeowners across Vilas, Oneida and Lincoln counties. I collected a sample of birds and shipped them to the wildlife health lab to confirm my suspicion of Salmonella. The reports of dead birds continued into Tuesday.
Is this another “aflockalypse?” No, unfortunately, we are seeing bird deaths from a combination of factors. When I speak with each caller, I discuss the importance of cleaning bird feeders and the ground around them. Most folks tell me they clean their feeders regularly, and I believe them. I think what we are seeing is a cumulative effect of the prolonged winter. Since the deaths are caused by a bacterium that is transmitted by bird waste, the bacteria likely does pretty well in the extended cool temperatures. It also probably persists in the frozen, crusty snow and ice beneath feeders, allowing birds to pick it up while in their normal feeding behaviors. Finally, the water that is open and available for them to drink here in town may be captured by ice underneath, which means the water can breed bacteria similar to a stagnant water puddle in summer. Add on an extended period of limited food and stressful conditions, and it seems likely that we are going to lose some birds. You can call my office at (715) 365-8999 to report five or more dead birds, but I do not need more samples at this time.
On a different note, an observant reader caught an error in last week’s article related to feeding deer and asked for a correction. I stated that the law allows placing two gallons of feed per day; that is not correct. According to law NR 19.60(2)(d)1., a person “may not place in excess of two gallons of feeding material within 50 yards of any owner occupied residence or business.” Sorry if this caused confusion for anyone.
Jeremy Holtz is a wildlife biologist with the Wisconsin DNR and writes a weekly column in the Star Journal. To contact him, call (715) 365-8999.