Tree swallows
September 10, 2014

Slim Bird Helps Researchers Answer Some Big Biological Questions

Jessica Arriens, NSF

International team of researchers studies one slim bird to answer some big biological questions

Ushuaia and Fairbanks are cities near the tips of the world.

The capital of Argentina's Tierra del Fuego province and the Alaskan metropolis don't have much in common. Except for a cluster of simple wood boxes on poles, and the scientists and swallows who flock to them.

Both animals are part of Golondrinas de las Américas--the Swallows of the Americas, an international research project studying the slight, swift swallow to answer larger questions about biological patterns.

"Looking at these birds across this huge hemispheric span of habitats provides a broader opportunity to explore relationships between the environment, temperatures and breeding," says David Winkler, a professor in Cornell University's Department of Ecology and Evolutionary Biology. He is the lead investigator for Golondrinas, funded through the National Science Foundation's Partnerships in International Research and Education (PIRE) program.

PIRE brings together U.S. and foreign researchers across all fields of science and engineering, supporting research advances that cannot happen without international collaboration.

That collaboration is especially crucial for the Golondrinas project. The team is studying causes of variation in the life histories of one genus of swallows, Tachycineta, which live throughout the Americas. "We wanted to dig in with a really full-blown exploration of all aspects of their breeding biology and ecology," Winkler says.

And for the last seven years, that's exactly what they've done. The site map for the project, affectionately known as Golo, spans the entire western swath of Earth: The Pacific stretch of California and Mexico, a sprinkling in Canada, the Midwest and the North Atlantic coast, then down through Central America and the Caribbean before spreading into Venezuela, Ecuador, Brazil, Peru, Chile and Argentina.

The Golo project has involved hundreds of students and interns--traveling in the U.S. and abroad--plus workshops, endless logistics, and collaborations with local residents and organizations. It's inspired graduate careers and supported conservation projects, weaving together an international swallow community.

"We were very ambitious," says Winkler.

Researching "ever-ready bunnies"

There are nine species of swallows in the Tachycineta genus. All are sleek, white-breasted birds with a metallic-sheened back, like they're dressed for an evening at the theatre.

Swallows are cavity dwellers, depending on other species to make homes for them. Woodpecker holes are a good choice, but so are the 5-by-5 inch nest boxes Golo uses. Swallows will readily nest in these rough wood homes, especially if other natural cavities are limited. Which means you can pretty easily create your own swallow population--one reason they make such good study subjects, Winkler says.

The other reason is that swallows are, for the most part, pretty resilient birds. "Once they find a cavity and start nesting, they're staying there," Winkler says. "I call them ever-ready bunnies ... as long as the food holds up and the weather doesn't get too bad, they keep trying."

At the various Golo sites, the researchers catch and measure individual swallows, monitor all aspects of the breeding season--from nest-building to chick counts--and take insect samples, to keep tabs on the swallows' prey. Protocols are detailed in the Golondrinas handbook -- "the Bible of how we do things," says Winkler--and results are loaded onto a shared database.

All this data will help answer some big questions: How does weather affect bird breeding at different latitudes? How do the birds vary physiologically across different regions? How much do tropical and temperate ecosystems--and changes in them--affect the reproduction, and ultimately the survival, of these birds?

The project addressed such fundamental ecological questions "via a broad network of international researchers comprised of ornithologists, entomologists, physiologists, educators, and avid birders across the Americas," says John Tsapogas, NSF program coordinator for PIRE.

"These interactions created a sustainable and synergistic research collaboration that has helped us better understand climactic influences on these birds and their insect prey."

Golo members recently published a paper in the journal Ecography, using 16,000 nest records from seven species--showing a connection between clutch size (how many eggs a swallow lays) and lay date (when she lays them) dependent on geography (variations in latitude).

"We're still analyzing a lot of data and I bet we will be for a while," Winkler says.

> Continue reading...