Faculty from northeast integrating universities collaborate on Tree Swallow nesting research

Anyone out walking in their yard or on a hiking trail has come across a bird’s nest and marveled at its construction.

Lauri Green, assistant professor of biological and allied health sciences at Bloomsburg University, is collecting the nests of tree swallows to evaluate nest construction to determine if there are any patterns to their construction. She's working with Leslie Clifford, associate professor of biology at Mansfield University, which is one of the three universities (along with Lock Haven) in the Northeast part of Pennsylvania which are integrating.

Also, working with Green is seasonal ranger Lydia Mohn from the U.S. Army Corps of Engineers at Blue Marsh Lake in Leesport, Berks County; Rhiannon Summers from the Department of Natural Resources at Ricketts Glen, Bloomsburg graduate students Eric Moeller, Mitchell Liddick, and Michael Facella; and Gabby Leonard, an undergraduate. New for the Fall 2021 semester will be Bloomsburg undergrads Rebecca Burlingame and Savannah Scherer.

“Tree Swallows and other species use the feathers of other species to construct their nests and form a ‘nest cup’ (where the eggs are laid and chicks are hatched),” said Green. “The literature suggests that feather linings help with temperature regulation and maybe as a parasite barrier for chicks. Though a few studies noted the number of feathers that Tree Swallows use in their nests, largely absent was any quantification of the feather sizes or types.”

After the nests are collected is when the real work starts.

“In Spring 2021, Leonard quantified the feathers used in Tree Swallow nests at my field sites,” Green said. “She meticulously counted, traced, and identified each feather. Tracing the feathers in a digitizing program tells us how big each feather was. She found that Tree Swallows seem to use different types of feathers at each site (some used large flight feathers, some used contour feathers). Interestingly, the total feather area for each nest (the sum of all the feather areas in each nest) was not significantly different across the sites.”

Clifford and Green first met as part of a discussion of faculty from the three universities interested in natural history. They soon found out they were both working on Tree Swallow research.

“I'm really excited to involve Mansfield University undergraduate students in this project because it will allow them to actually do science themselves and not just learn about the results of scientific investigations by others,” said Clifford. “It's much more exciting to be able to discover patterns and answer original questions for yourself than it is to be told what the answer is. We generally learn best by doing something, so this hands-on research experience will provide students with a wonderful learning opportunity that will enhance their education.  My hope is that once my students learn the Tree Swallow system and begin to answer the questions that Lauri (Green) and I have posed, they will start to come up with their own original questions about tree swallow nests and pursue them.”

“We are going to repeat the study for the 2021 field season,” said Green. “Dr. Clifford is working with her undergraduate students to count, measure and identify the feathers used in her Tree Swallow boxes. I will begin the analysis of our nests soon. Anecdotally, Dr. Clifford’s nest boxes are smaller, so the sizes of the feathers appear to be smaller.  Up at Blue Marsh Lake, they also have small nest boxes, but many of the feathers used in the nests appear quite large.”

Green’s work, she hopes, will answer a variety of questions about the construction.

• Do the numbers and sizes of feathers used by Tree Swallow vary across sites and habitat types (wetland vs. riparian for example)?
• Do Tree Swallows aim for a specific feather area to nest volume ratio in their nests?
• What types of feathers are they using (flight, contour, downy)?
• What species of bird feathers are Tree Swallows using (are they targeting certain species or just picking up what is available)?
• Do differences in feather lining affect chick survival?
• In the long term, we plan to partner with other Tree Swallow researchers in PA and hopefully across the country to evaluate broadscale patterns.
• In the long term, will feather linings change as the climate warms?
• In the long term, will feather linings change as the sources of the feathers from migratory birds change?

Leonard learned a lot as part of the research team.  

“I thought it was cool to see the type of habitat the Tree Swallows prefer first hand, which I also thought to be relevant when the differences/similarities between the nests across the different nesting sites were compared,” said Leonard. “It was super interesting to see that there was consistency in how the birds made their nests despite some observed differences between nesting sites. As a student, collecting and compiling the feather and nest data was very tedious (and messy), but I enjoyed my research experience, and the topic of this project was aligned with my interests.”

Green is concerned about one aspect of nest construction she is starting to come across.

“I happened to pick up an old Robin nest recently and found that they included plastic in their nests. This is intriguing and concerning since plastic will likely change the temperature regulation of the nest, which would impact chick survival.”