Normally, birds like cardinals, chickadees and mourning doves would not be eating in one place, all the time, together.  

Humans change that behavior when we put up bird feeders.  

By doing that, we also increase the risk of disease spread, says Todd Schneider, wildlife biologist with the Georgia Department of Natural Resources.

“A lot of the diseases that can affect bird populations can be transmitted at feeders,” Schneider said. “What you're doing is bringing them in close proximity, some species that normally wouldn't associate.” 

For example, eastern house finches can catch mycoplasmal conjunctivitis, caused by a respiratory infection.

And every year, wildlife biologists see songbirds get sick from salmonella bacteria, specifically with salmonellosis, which causes lethargy and messes up the bird's intestinal track, making eating nearly impossible. Once caught, it's usually fatal. 

"They try to eat, but they can't swallow the food," said Sonia Hernandez, professor at the University of Georgia and with the Southeastern Cooperative Wildlife Disease Study.  “Sometimes it progresses very quickly into sepsis, and so then the bird can just simply drop dead." 

Hernandez said outbreaks typically happen in the winter, possibly because humans like to put out food in the colder months, when birds seem the most vulnerable. When birds carrying the bacteria in their system start to congregate, that’s when disease can spread.  

Bacteria are transmitted from contact with fecal matter and can infect a bird with salmonellosis within a couple of days.

It’s easy for a bird to come in contact with the bacteria from a platform bird feeder or a bird baths, Hernandez said.  

For any bird feeder setup, what’s widely agreed upon is that it’s important to clean up the feeder and remove what gathers under it, every few weeks, since birds defecate where they eat.  

Schneider said there are also some red flags to especially consider. For instance, is the bird feeder in an area that stays wet? Or are there multiple feeders near each other?   

“That's a good environment to breed bacteria,” he said.  

With multiple feeders, moving them even 20 feet away can help. Getting rid of the seed hulls left over from birds that just want the kernel is important too, since those hulls can be a reservoir for bacteria growth.  

“The area where they're pooping, basically in the seat hulls are falling, that's going to be where the organisms build up,” Schneider said. That includes some type of fungi.  

And since humans can get sick from these bacteria too, they should wear gloves and maybe a mask when handling bird feeders and cleaning them. Schneider suggests using a bleach and water solution at a roughly 1 to 10 ratio.

 

There's more work to do in mapping illnesses in birds 

It’s likely many cases of salmonellosis in songbirds go unreported, since they’d require people to tell their local public health districts.  

And there are still questions about whether some birds are more susceptible to illness from salmonella bacteria than others, or in cases of outbreaks, if some species can be reservoirs, meaning they carry a disease and can spread it but are otherwise asymptomatic.  

Answering these questions is mostly a priority if it affects human public health, Hernandez said. A surge in research on zoonotic diseases could help fill in gaps in data.  

“One of the only positive consequences of Highly Pathogenic Avian Influenza is that it's got everybody talking about bird health,” Hernandez said.  

HPAI, the disease commonly known as bird flu, has wreaked havoc on wild bird populations since 2022. The virus has been detected in some species of crows, owls, geese, seabirds and most recently, several mallard ducks. 

But songbirds are not considered “important players” in the disease epidemiology, Hernandez said. Research has found that some carry HPAI antibodies, meaning they were infected, but the virus wasn’t fatal.  

HPAI has been fatal to over 100 million chickens in the U.S. and continues to infect chickens across the country, causing a surge egg prices and leaving many farmers without their primary moneymaker. The outbreak also puts farm workers at risk, and has led to the death of one person so far. 

Current guidelines on biosecurity for commercial and small flock chicken owners is to keep chickens separate from other bird species as well as being mindful of virus transmission through human movement, by keeping clothes, shoes and equiptment clean, to limit possible spread.  

Tags: bird flu  birds  avian influenza  salmonella  zoonotic diseases  Georgia  wildlife biology