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Black Swift Mystery 🪶

by Dr. Oakleigh Thorne, II

Black Swift (Cypseliodes niger borealis)

The Northern Black Swift (Cypseloides niger borealis) is a mysterious bird that nests during the summer in western Colorado, usually in moist caves and in canyons near waterfalls. My fellow graduate student friend, Owen A. “Al” Knorr, back in the late 1940s and early 1950s, studied these amazing birds for the Denver Museum of Natural History as part of his doctorate degree at the University of Colorado in Boulder. Up until then, little was known about Black Swifts. Al uncovered many secrets and interesting facts about these fast-flying birds.

Similar to swallows, swifts feed on flying insects, so they are constantly “on the wing” catching their prey in mid-air. Because of this diet, they must always be where there are flying insects, so they have to migrate to where there is “perpetual summer,” somewhere way south of Colorado, but where? For many years, nobody knew where Black Swifts went during our winter.

In 1998, the late Rich Levad, then head of the Rocky Mountain Bird Observatory (RMBO), became excited about studying Black Swifts. He also got other bird researchers interested in studying them. For four years before he died, Levad spent his time writing a book titled: The Coolest Bird: A Natural History of the Black Swift and Those Who Have Pursued It.

Birds that breed in the U.S and Canada and spend their winter months in Central or South America are called “neotropical migrant bird species.” Neotropical is a cool word for you to learn! But nobody knew exactly where the Black Swifts went when they left Colorado in late September or early October and returned here again in late May or early June. This was a mystery yet to be solved.

A team of three scientists, who were inspired by Levad, set out to find where the Black Swifts migrated. They were Jason Beason, who replaced Levad at RMBO, Carolyn Gunn from the Colorado Division of Wildlife, and Kim Potter with the U.S. Forest Service. This team was able to buy very small “geolocators” and invented tiny “backpacks” that they strapped on the backs of four Black Swifts that they were able to capture in nets during the summer of 2009. They used narrow strips of Teflon to hold the “backpacks” securely on the backs of the birds, then they released them.

A year later, in 2010, when the swifts returned to nest, the trick was to try to recapture the same four birds. Black Swifts usually build their nests in the same locations each year, so the team was able to catch three of the original four birds! They then downloaded the information from the geolocators. It took them many months to analyze the data and figure out where the birds had been. They had recorded the length of day from sunrise to sunset. From this they were able to learn the exact location (latitude and longitude) of the birds from day to day. The swifts had flown to western Brazil for the winter! They had gone about 4,300 miles, or 244 miles a day on their way to Brazil and 211 miles a day on their way back to Colorado. Instead of going to mountains that were similar to Colorado’s, they had instead wintered in the lowland rain forests of Brazil.

Isn’t it exciting to learn of this special research about the Black Swifts? You can grow up to be a scientist, too, and do similar interesting research. I hope you do!

Dr. Thorne is founder and honorary president of Thorne Ecological Institute in Boulder. They have helped “connect kids to nature” for more than 55 years. For more information about Thorne Natural Science School classes for children, check or e-mail or call (303) 499-3647.

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