HARD TO SWALLOW

Researchers in British Columbia and at the Woodland Park
Zoo in Seattle, Washington, investigate the recent and
rapid decline in swallow populations in North America.

Story by Chuck Tookey| Photos by Matthew Pearson

Gretchen Albrecht holds a swallow that was caught in a special net she uses to catch and examine local swallows. Albrecht has worked at the Woodland Park Zoo for almost two decades and has noticed an alarming decline in the populations of swallows that nest at the zoo.

Gretchen Albrecht watched four barn swallows dart across the sky, cresting tree tops in a fighter-jet like formation. Albrecht is a raptor keeper at the Woodland Park Zoo in Seattle, Washington who has studied the barn swallows living there for 18 years.

“They’re very falcony,” Albrecht said as the barn swallows twisted and turned through the air, sunlight reflecting off their iridescent blue feathers. The awe hasn’t left her voice even after almost two decades of studying swallows.

“They’re beautiful little birds,” she said.

OVER THE PAST 14 years, Albrecht has noticed a significant drop in the number of barn swallows nesting at the zoo. In 2004, there were nine active swallow nests in the zoo’s Raptor Barn and 13 in the Cow Barn. This year, those numbers have dropped down to only two and three, respectively. Barn swallows are migratory birds, some flying over 17,000 kilometers to and from their northern breeding grounds every year. They nest in man-made structures each spring and have raised their young alongside humans for generations. Barn swallow populations have steadily declined around North
America for the past 50 years. This has been a common trend for many aerial insectivores, birds that hunt and eat insects mid-flight. It is likely human activity, such as the destruction of habitat and climate change, has played a large role in causing these population declines.

“We have sites that were active for eight years of the study that don’t have barn swallows, they just didn’t come back,” Albrecht said. Like Albrecht, George Clulow, an active member of the birding community in Vancouver, British Columbia, has witnessed the aerial insectivore population decline. This year, on one morning in mid-April, he counted about 75 swallows of two different species at Deer Lake in Vancouver.

Above, left and right: Albrecht retrieves swallows from a mist net at the Woodland Park Zoo in Seattle, Washington. She has studied swallows for years to help identify any significant changes in the species. Bottom: Albrecht holds a swallow at the Woodland Park Zoo in Seattle, Washington. She has noticed a decline in the numbers of barn swallows at the zoo.

“A typical morning at the same time of year, say 10 years ago, would have recorded 400 swallows of four or five different species,” Clulow said.

Barn swallows have a very close tie to people. The beams and ledges of man-made structures in Europe, North America and Asia have been used by swallows as nesting sites for thousands of years.

“They will live right in our midst. It’s like they don’t care we’re here,” Albrecht said. “Anybody can enjoy them. They just show you their whole life.”

Keith Hobson, a professor and researcher from Western University in Ontario, Canada, worked with Albrecht at the Woodland Park Zoo to study barn swallow migratory paths. Hobson explained that as weather events become more extreme and unpredictable due to climate change, swallows are more likely to encounter storms that could lead to starvation during their
migration.

In the study, Albrecht and Hobson attached miniature light-sensitive geolocators, weighing half a jelly bean, to barn swallows, allowing them
to track the birds throughout their migration. They found that these teacup-sized birds fly from Seattle to as far south as Panama, and from New Brunswick, Canada to as far south as Argentina. Sections of these migration paths can involve 640-kilometer, non-stop flights over open water, twice the distance between Bellingham and Portland. With climate change, weather conditions in the barn swallows’ northern breeding grounds are no longer
as predictable. They might arrive after their journey to comfortable spring weather, only to be hit with snow storms a few days later, Hobson said. These severe weather fluctuations hit swallows hard because aerial insects are their
main food source and the bugs they eat don’t fly in the snow. Swallows may go dangerous amounts of time without eating as weather becomes increasingly unpredictable.

“They just have to hope that they can make it through the cold snaps. They really commit themselves. There’s no going back,” Hobson said.

In addition to facing unpredictable weather, barn swallows now face unpredictable nesting conditions in their breeding grounds. As agriculture in North America has shifted from small local farms to massive industrial operations, the old buildings barn swallows have nested in for years are being replaced with new uninhabitable ones, according to the 2012 State of Canada’s Birds report.

Albrecht explained barn swallows frequently return to the same nest year after year. They make their nests on small, flat surfaces in high places using mud, grass and feathers. The nests are sturdy and can be reused for as long as 15 years with the occasional touch-up. At the Woodland Park Zoo, nests could be seen all around the Raptor Barn. From high pipes running along the walls to the lights on the ceiling, examples of swallow construction skills were on display. Now, the majority of these nests are empty.

“Swallows, like all animals, are uniquely adapted perfectly to what they do best,” Hobson said.

Swallow populations are steadily decreasing in many habitats, but Burnaby Lake in British Columbia still provides habitat for hundreds of them.

Barn swallows migrate thousands of kilometers and feed almost exclusively on insects caught while flying. They have adapted to human impacts on the planet by nesting in buildings and adjusting to landscape change, Hobson said.

Clulow explained barn swallows and humans have a supportive relationship. The fields and structures made by humans have historically provided perfect hunting and nesting grounds for swallows. In return, barn swallows have provided insect reduction services for farmers and gardeners.

“There is a direct connection between the way birds act and the way humans act too, it’s very close,” Clulow said.

Barn swallows have ingrained themselves into human society, which makes them a very easy species for people to connect with. This opportunity to connect with the natural world is being lost as fewer barn swallows return each year to breed. According to the North American Breeding Bird Survey, in the past 40 years, barn swallow populations have declined by 50 percent
in North America, and in British Columbia alone, populations have declined by 89 percent.

“It’s not just good enough anymore to worry about what happens in our backyard,” Hobson said.

Albrecht and her fellow raptor keepers at the zoo reminisce about the days when the nests in their barn were all occupied. Albrecht pointed to one nest on a light above her head, remembering the swallow who came back to it eight years in a row. She joked about the swallow drama her and her colleagues noticed, and laughed about the time a pair of swallows built a nest on a fire extinguisher because all the other nests were taken.

Swallows rest on a branch near Burnaby Lake in British Columbia. Burnaby Lake provides habitat for swallows despite the declines that have been seen elsewhere.

Perhaps Clulow put it best when describing the worth of barn swallows.

“They have an intrinsic value, just like a great work of art has an intrinsic value,” he said.

“Yes, we can put a monetary value on a piece of art but when it’s hung in a museum for the appreciation of everyone, it has a value that is not simply measured by dollars.”