A Swallow’s Tale
A 35-year study of cave swallows at Carlsbad Caverns has solved some abiding mysteries about the songbird.
On a sunny afternoon last July, Steve West, a fit man in his 60s with white hair, a mustache, white hair, glasses, and a quick smile, loitered about the visitor center at Carlsbad Caverns National Park. Looking like an absent-minded professor, he carried two long, skinny aluminum poles and appeared to be searching for something. But West wasn’t lost. He was looking for volunteers to help band cave swallows inside the park’s namesake cavern for a special research project.
By the time he gathered about ten people, the cave entrance had closed to visitors for the evening. With special permission from the Park Service, the group descended from rocky desert studded with sotol, yucca, and prickly pear into the cool serenity of the cave’s massive, gaping maw, stopping at the narrowest part of the entrance chamber about 100 feet down.
With the fine net strung between the poles, the volunteers sat in silence as birds flew in and out of the cave, tangling themselves in the mesh. Then came the fun part: After lowering the net, West and longtime volunteer David Culp demonstrated how to pluck a swallow from the nylon web. West held it gently in the palm of his hand, affixed a band to its ankle, and called out the sex, salient characteristics, and measurements of the quivering one-ounce bird to volunteers waiting with clipboards.
“The little ones tend to be feistier, and sometimes they’ll try to peck you, which is incredible because they’re such tiny little birds and they’re so brave!” says Georgina Jacquez, a park guide who regularly helps band birds. “Sometimes they’ll just lie there and look at you, and you can feel their breathing and their hearts racing. For visitors, it’s a really neat opportunity to have a bird in hand, and to contribute to the science that’s going on in the park.”
LUCK OF THE SWALLOW
Unlike other species, cave swallows benefit from human settlements, which offer new roosting spots, such as bridges, buildings, silos, and culverts. Agricultural fields also attract insects and create feeding grounds for the birds, which is why cave swallow populations in the United States have increased over the past 30 years.
When West, a high-school science teacher and avid birdwatcher from nearby Loving, New Mexico, began banding cave swallows in 1980, they were one of only three migrating American bird species whose wintering grounds remained unknown. Since then, every year, volunteers have helped West capture and release swallows in one of the longest-running bird-banding studies in the country. To date, more than 5,000 volunteers from 42 states and 20 countries have participated, helping to band nearly 23,000 birds. Along the way, they’ve helped West—also a volunteer—to compile research that has profoundly improved scientists’ understanding of this charismatic songbird, known for its lively calls and dramatic dives.
Among his findings, West has discovered that most cave swallows live between three and five years but in rare cases can live as long as 13. He has learned details about their range in size, food habits, sex ratios, common parasites, and responses to a host of environmental conditions, such as rainfall and temperature. He even solved the alluring mystery of where they go in the wintertime.
The first clue came one morning in 1992, when West received a letter from the U.S. Fish and Wildlife Service informing him that a retired postal worker in Jalisco, Mexico, had reported finding a dead bird on his front porch, with a mysterious silver band on one leg. Thanks to West’s own trips to Panama and El Salvador as well as observations from other researchers in unexpected habitats like mangrove swamps and sugarcane fields, it’s now clear that the cave swallows winter as far as the Pacific Coast between Mexico and Costa Rica.
“In a scientific study, you have to develop patience, because if we had gone down to Carlsbad Cavern and banded birds for three years and left, we wouldn’t have learned very much,” says West, who used the swallow research to earn a master’s degree in science education at New Mexico Tech.
Sometimes the work is harrowing. In 2011, a rare ten-day freeze and the effects of a drought and a forest fire decimated the population of baby birds. West banded a measly 23 fledglings in comparison with the 250 to 350 he normally bands in a year. “I’m getting into some anthropomorphic territory here, but that was really sad,” he says. The next year, however, he was surprised to learn that the birds were remarkably resilient, bouncing back to produce normal broods of hatchlings.
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The information not only reveals characteristics of individual birds and whether the hatchings had access to enough food, says park guide Georgina Jacquez, but also unearths trends that might crop up because of environmental factors. And information on where the birds travel in winter can help park managers respond more effectively if the population declines, says the park’s supervising biologist, Renée West. Park guides like Jacquez have also shared details of West’s research with park visitors, who love to watch the birds swoop and dive into Carlsbad Cavern in the evenings, just before the bats emerge.
West plans to continue banding cave swallows because so many questions about the species remain unanswered. For example: Why do the adults lose and regenerate all their feathers before the fall migration? And why do some females spread the scent of a local beetle on their bottoms? The continuing banding excursions, typically run on Fridays between March and October, also offer an opportunity to ignite volunteers’ interest in parks by experiencing the wildlife in an intimate way.
“When you actually pick up a bird from the net and hold this little feathered guy in your hand that can fly forever, across countries and continents, it’s pretty amazing,” says local volunteer Leonel Pando. “Doesn’t everybody want to get up in the sky and fly like a bird?”
About the author
Kate Siber, a freelance writer and correspondent for Outside magazine, is based in Durango, Colorado. Her writing has appeared in National Geographic Traveler and The New York Times. She is also the author of “National Parks of the U.S.A.,” a children’s book.