Birds spread infections at feeders, according to ISU research

AMES, Iowa – Diseases may spread faster in birds that visit bird feeders frequently, according to new research from an Iowa State University ecologist.

A study of house finches in Virginia found that birds that often visited feeders were more likely to spread an eye infection called mycoplasmal conjunctivitis. The research, published this month in the academic journal the Proceedings of the Royal Society B, offers new insights into how diseases spread among birds.

two house finches at a feeder

House finches visit a bird feeder. Photo by Bonnie Fairbanks and courtesy of James Adelman. Larger image.

“If you’re interested in reducing the incidence of a disease, understanding which individuals are likely to transmit pathogens is critical, especially when transmission might be taking place literally in our backyards,” said James Adelman, lead author of the study and an assistant professor of natural resource ecology and management at Iowa State.  

The research team tagged house finches with tiny transponders and tracked their activity at various bird feeders. These observations showed that birds that spent the most time at the feeders were more likely to contract the infection.

The team also studied small flocks of house finches in captivity and kept track of which birds spent the most time visiting feeders and which ones spent the least time. The results complement the findings from monitoring wild birds. Experimentally infected birds that spent a lot of time at bird feeders were more likely to spread the infection, while infected birds that spent less time at the feeders were less likely to be disease vectors.

photo of small tags used to track finches

Researchers used small tags attached to the feet of finches to track how frequently they visited bird feeders. Photo by Greg Fisk and courtesy of James Adelman. Larger image.

The researchers chose mycoplasmal conjunctivitis, an infection similar to pink eye in humans, for the study because its visible symptoms are easy to recognize and record.

But Adelman cautioned against removing backyard bird feeders, even in light of the findings. The feeders provide plenty of health benefits for birds, including a source of sustenance during lean winter months.

“The overall health outcomes related to bird feeders are likely quite good,” he said. “They can help birds maintain weight and good health, especially in the winter.”

Rather than removing feeders, Adelman recommended that feeders be disinfected regularly to combat the spread of pathogens.