November 16, 2017
By Iriel Edwards, College of Agriculture and Life Sciences, Cornell University, Class of 2020
When it comes to providing for our backyard birds, we want to help them along through rain or shine. Most people want the best for our flying friends, and leaving out a tray or feeder with seed can be a very rewarding method of giving them a boost of resources. But one thing that may cause concern is the potential for our bird feeders to spread disease. New research looked into the potential for bird seed to facilitate the spread of a parasite called Trichomonas gallinae, which can be harmful to birds such as pigeons, doves, and finches. Normally it is transferred from an infected bird through bodily fluids, but could wet seed be a way of transmitting it as well? Researchers wanted to determine if this parasite could persist in bird seed, outside the body of a bird. What they found is good news for all of us feeding birds: the parasite can survive but only in very limited and preventable conditions.
Can the parasites survive outside a host?
A group of Canadian researchers gathered three popular types of birdseed (mixed seed, black-oil sunflower seed, nyjer seed) and created wet and dry versions of each seed type. A low concentration and a high concentration of T.gallinae was added to each type of seed in its dry state and in its wet state. These samples were monitored in very warm conditions (98 degrees F) for more than ten days to see if the parasite could survive outside the body of a bird host.
The researchers found that the parasite was able to persist only in wet seed and only for a couple of days at most. It remained in the wet mixed seed sample the longest (for 48 hours) because the organic matter such as wheat and peas present in most commercial mixed seed was good at retaining water. The best news? No signs of the parasite were recovered from the dry seed samples.
Cleaner, safer feeders
Understanding this parasite’s ability to persist in the food we provide to wild animals is important in preventing avian outbreaks. What we learned from this work is that by keeping seed dry, you can prevent this parasite from persisting. Even if seed is wet, the parasite was only able to persist for a short time at temperatures comparable to the inside of a bird’s body, so it is likely that in cool conditions there is very little risk from T. gallinae. This finding means you need only be concerned if you are feeding birds damp seed in a warm and humid climate. Here are some tips on how to provide a safer feeding source to your backyard friends:
•Keep your feeder out of the “splash zone” of any nearby birdbaths or drinking stations
•Consider bringing your feeder in before a heavy rain if temperatures are very warm.
•Change your seed out regularly if you are in hot and wet weather conditions.
•Choose seed types that contain little to no organic material (buckwheat, peas, and sorghum), e.g. nyjer seed or black-oil sunflower seed.
All in all, you shouldn’t be afraid to offer a batch of seed to a hungry flock of birds. However, it is important that we stay mindful of the roles that we play in other creatures’ lives. Let’s cherish the relationship we have with backyard birds by sharing with them a clean and dry meal!
Research reported in: Persistence of Trichomonas gallinae in Birdseed (2017). Scott McBurney, Whitney K. Kelly-Clark, María J. Forzán, Raphaël Vanderstichel, Kevin Teather, and Spencer J. Greenwood. Avian Diseases Vol. 61, No. 3: 311-315.