FEBRUARY 4, 2020
If you feed the birds in your backyard, you may be doing more than just making sure they have a source of food: you may be helping baby birds give parasites the boot.
New research published in the Journal of Applied Ecology from UConn assistant professor of ecology and evolutionary biology Sarah Knutie shows that feeding bluebirds can have a significant impact on parasitic nest flies feeding on baby bluebirds.
Parasitic flies can be found in the nests of many bird species, and some can have significant impacts on nestling survival.
The flies lay eggs in the nests, and once the eggs hatch, the larvae feed on the blood of nestlings by drilling holes through the young birds' skin.
In the case of bluebirds, Knutie says it appears nestlings are generally tolerant of the flies, meaning they can sustain high loads of parasites but not suffer significant negative impacts on survival and growth. However, the parasite removes a lot of blood from the nestling, which could have lasting impacts.
"Bluebirds do not have a detectable immune response to the parasitic flies," says Knutie. "Since backyard bird feeding by humans is so popular, I was interested in how giving these birds food could influence their immune response against the parasite, and whether there is a particular time during the breeding season when supplemental feeding is most effective."
To perform the study, Knutie and her father set up 200 nest boxes in northern Minnesota. She followed each nest for the presence of bird eggs, and then, when the eggs hatched, fed some of the birds live mealworms.