Secrets and techniques of Joint Nighthawk Migration with GPS Monitoring Unlocked


A new study, led by the Smithsonian Migratory Bird Center and University of Alberta biologists, used GPS data to create a comprehensive picture of the 10,000-kilometer migration route of night owls. The study, published February 2 in Ecography, is the first step in analyzing where and why night owl populations are declining.

“This charismatic migratory bird – known for its evening dances to catch insects – is one of many species whose name includes the word ‘common’ even though they are disappearing from parts of their range,” said Autumn-Lynn Harrison, research ecologist at the Smithsonian Migratory Bird Center. “Our international partnership has shown the previously unknown migration routes of night owls as an important step in planning their recovery.”

The night hawk is one of the most widespread birds in the western hemisphere, but also one of the least understood due to its nocturnal nature. Not a hawk at all, but a member of the nightjar family – a group of nocturnal birds called “falcons” to catch and eat flying insects.

“Like many migratory bird species, the night hawks are declining, but the rate of that decline varies across North America,” said Elly Knight, lead author and PhD student in the University of Alberta’s Department of Biological Sciences. “For migratory species like the night hawk, figuring out what is causing these declines can be difficult and complicated because they occupy so many different locations throughout the year.”

The project brought together researchers from the Smithsonian Migratory Bird Center, the University of Alberta, and Environment and Climate Change Canada in a massive collaboration across 13 locations across North America. In the summer months, the researchers equipped night owls in North America with small backpacks with GPS transmitters. The researchers sought a complete picture of the common night hawks’ migration connectivity, that is, the degree to which birds from different populations stick together during their migrations.

“This is a critical start in developing conservation approaches as we can focus on the times and places where population decline might occur,” said Knight, who completed the research under the direction of Professor Erin Bayne. “Without an understanding of migratory connectivity, there are myriad possible reasons why a migratory species could decline. Without the full picture, we could miss times and places where population declines occur. “

Common night falcons breed in North America, but migrate up to 10,000 kilometers south into the Amazon and Cerrado biomes of South America in autumn. The birds make numerous stopovers on their journey, and GPS location enables biologists to understand where and when they spend their time outside their breeding grounds.

“We were surprised that while revelers, while common across North America, use essentially the same migration route to their wintering grounds in South America,” Knight said. “All breeding populations fly east or west to congregate in the American Midwest along what is known as the Mississippi migratory route. From there they all mingle and take a common route south across the Gulf of Mexico, down through the northern Andes and into their wintering areas, mostly in Brazil. This common route means that outside of the breeding season there are only a few train connections for night owls. “

“Now that we understand common migratory connectivity of night hawks, we can take the next steps towards understanding the limits of their populations,” Knight said. “We plan to focus on the times and places of increased connectivity: brood, fall migration in North America, and before crossing the Gulf of Mexico during the spring migration.”

Researchers will compare hypotheses about the possible causes of declines that might occur in these areas and relate them to population trend data to see what explains the differences in trend between populations.

This collaborative project involved 29 researchers from 17 organizations and many volunteers from the Smithsonian’s Migratory Connectivity Project. The project was led by researchers from the Smithsonian Migratory Bird Center, University of Alberta, and Environment and Climate Change Canada. Large funding has been provided by the Natural Sciences and Engineering Research Council of Canada (NSERC), Environment and Climate Change Canada, and ConocoPhillips.

Via the Smithsonian Migratory Bird Center

The Smithsonian Migratory Bird Center (SMBC) is dedicated to understanding, conserving, and promoting the great phenomenon of bird migration. Founded in 1991 and part of the Smithsonian Conservation Biology Institute (SCBI), SMBC scientists work to protect migratory bird species through research and public education that promote better understanding of migratory birds and the need to protect various habitats in the Western Hemisphere. SCBI plays a leading role in the Smithsonian’s global efforts to save wildlife and educate future generations of conservationists, leading research programs at its headquarters in Front Royal, Virginia, Smithsonian’s National Zoo in Washington, DC, and field research stations Training locations worldwide.

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