Have a bird feeder? It might be spreading pink eye

It's fun to watch birds swoop in for lunch at your backyard bird feeder, but these avian fast-food stops could actually be helping spread disease.

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.

"Our results suggest that in this species, a few individuals -- those that like eating at feeders -- are likely very important in driving disease epidemics," said Dana Hawley, a co-author on the study and a member of the Global Change Center at Virginia Tech. "If this is true for other wildlife species as well, we may be able to more effectively reduce disease by targeting these high risk individuals."

The research team tagged house finches with transponders and tracked their activity at various bird feeders. 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.

"This technology enabled us to capture where birds fed during the winter and who they chose to feed with," said Sahnzi Moyers, a doctoral student at Virginia Tech, who works with Hawley.

That same data was also used to reconstruct the birds' social networks. Birds that were frequently seen together had stronger bonds. Based on previous work, the authors expected that birds that had many connections would be more likely to be exposed to the disease and to spread it.

"We expected birds that were more central in the social network, or had more friends, to catch the disease, because previous research has found that this was important for accessing information about where food is located. But, we found instead that it was birds' feeding preferences that were most important," said Damien Farine, a postdoctoral researcher with a joint appointment at the University of Oxford and the University of California-Davis and co-author of the study.

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. They didn't say whether similar findings might be found with diseases that are more dangerous to humans, such as bird flu.

But just because the feeders increase infections, that doesn't mean they should be tossed out. The feeders provide plenty of health benefits for birds, including a source of sustenance during lean winter months, according to Iowa State's James Adelman, the lead author of the study.

"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 they be disinfected regularly to combat the spread of pathogens.