Feeders can spread dangerous diseases to birds. Here's what you can do.

Backyard bird watching is a simple pastime for millions of Americans. More than 40 percent of U.S. households buy bird seed for their feeders at home, and that number is expected to grow, according to an industry research study.

But there may be a darker side to backyard bird feeding. According to an extensive, 25-year-long study from the British Trust for Ornithology, Fera Science and the Zoological Society of London, bird feeders can spread a number of dangerous diseases among wild birds.

The study primarily looked at diseases affecting wild birds in Britain, but it has implications for America too. The U.S. Geological Survey recognizes four common diseases that commonly affect birds that use feeders, some of which are the same diseases the British study found in their birds, and all of which can lead to death.

The scientists looked at 25 years worth of data from the Garden Wildlife Heath program, which allows residents to submit information about how birds, reptiles and other backyard creatures are doing. They found clusters of disease among wild birds that used some backyard feeders.

“Our study shows how three of the most common diseases that affect British garden birds have changed both dramatically and unpredictably over the past decade, both in terms of the species they affect and their patterns of occurrence,” said Becki Lawson, a lead author of the study, in a press release.

The scientists found that birds could get diseases like finch trichomonosis, Paridae pox and passerine salmonellosis. Some of the illnesses appeared to be at epidemic levels, while others - like salmonellosis - are at much lower levels.

‘These conditions have different means of transmission – so deepening our understanding of disease dynamics will help us develop best practice advice to ensure that feeding garden birds also helps to safeguard their health,” Lawson said.

There are a few ways these diseases can spread at feeders: many birds who would not normally cross paths in the wild can find each other at the feeder, University of Georgia researcher Daniel Becker told Audobon, providing “ideal conditions for parasites and other contaminates.”

If the feeder is dirty or the food is stale, that can also cause problems, the scientists said. But none of this means you have to tear down your feeder in despair. Scientists say bird feeders are helpful, especially in the winter months when a reliable food source is important.

But there are a few ways backyard birdwatchers can provide food for the birds while also keeping them as healthy as possible.

“We’re calling on everyone who feeds wild birds to be aware of their responsibilities for preventing disease,” the study’s co-author Kate Risely wrote in a release.

Simple steps they recommend include:

• offering a variety of food from accredited sources
• feeding in moderation, so that feeders are typically emptied every 1-2 days
• the regular cleaning of bird feeders
• rotation of feeding sites to avoid accumulation of waste food or bird droppings

Just as well, if you notice birds acting sick, pull the bird feeder for a few days, make sure it’s clean and check to make sure the area is clear of waste and seed droppings. Sick birds look lethargic, cower on the feeder, have ill-kept feathers and are often reluctant to fly, the USGS says.

“Certainly, the signs of illness are not as easily noticed as bright colors and cheery songs; but being inconspicuous does not make disease unimportant,” the agency wrote.

The researchers said it was important for their to be a “balance” between the benefits of feeding wild birds and the risks. As long as that balance is there, it should be fine to keep watching out the window - just know that you might need to do a little more legwork to keep your avian companions healthy.

This story was originally published March 12, 2018 at 9:49 AM with the headline "Feeders can spread dangerous diseases to birds. Here's what you can do.."