Researchers link spread of avian disease to bird feeders

Many Canadians set up backyard bird feeders, especially when the winter months approach. The feeders provide a reliable food source to birds that brave the north instead of flying south. But a new study shows bird feeders could actually be helping to spread avian disease. Researchers from Virginia Polytechnic Institute and University suggests birds that visit feeders are more likely to catch and then spread deadly avian diseases.

"It's a lot less likely for a number of different birds to all go to the same flower or fruit in close proximity. Whereas with a bird feeder you're attracting a number of different birds at high densities to come to the same place and be exposed to the same surface," Dana Hawley tells As It Happens host Carol Off.

Hawley is an Associate Professor of Biological Sciences at Virginia Tech and lead researcher on the study. High traffic bird feeders accumulate a variety of pathogens but Hawley is particularly interested in conjunctivitis, an eye infection, and its effect on the house finch, a common songbird.

"The sick birds, when they have itchy eyes, they rub their eyes on the port of a bird feeder while they're feeding and they leave bacteria that can then be picked up by the next healthy feeding bird," Hawley explains.

In order to track the behaviour of the house finch population, Hawley used barcode tags on the birds, that automatically sent a signal to antennas that were attached to the bird feeders. 

"Each bird had one of these tags, it's about the size of a grain of rice, attached to their leg bands."

With this method, the researchers recorded the feeding habits of the birds over a winter. The study showed that the finch population dropped by approximately 50 per cent because of conjunctivitis.

"It has brought down the population and the population has stayed at a smaller size because of this disease," Hawley explains.

Despite the findings, Hawley makes it clear that she is not suggesting bird enthusiasts take down their feeders. She stresses the vital role feeders play in providing food resources for the birds during the scarce winter months.

"It's kind of a paradox because house finches are really in our backyards precisely because of bird feeders but bird feeders also have a slightly negative effect on their populations. On the whole I think bird feeders do house finch more good than they do harm."

Hawley recommends cleaning the feeder regularly to reduce the risks of spreading the pathogens.

"It's good to sanitize your feeder as often as you can."