Meredith Gutowski, Manomet Center for Conservation Sciences
This past spring, a 6-ounce Red Knot (Calidris canutus) – a shorebird only two-thirds the size of a city pigeon – flew non-stop for six days and nights, covering 5,000 miles (8,000 kilometers) across the Amazon and the Atlantic Ocean between southern Brazil and North Carolina, shattering the previous known Red Knot record by nearly 700 miles. Late in the previous summer, the same Red Knot flew non-stop for eight days between Canada’s Hudson Bay and the Caribbean.
These are two of the fascinating results just published in the bulletin of the International Wader Study Group by a group of shorebird researchers from the United States, Canada, Argentina, Britain, and Australia. Lead author Dr. Larry Niles, a scientist with the Conserve Wildlife Foundation of New Jersey, and his colleagues employed a relatively new technique – sunrise- and sunset-sensitive geolocators attached to the legs of Red Knots in New Jersey – to shed new light on the annual migration of this species of special concern. Red Knots winter as far south as Tierra del Fuego, South America, and breed in the Arctic.
From May 2009 to May 2010, a Red Knot (data-name, “Y0Y”) flew a record-breaking 16,600 miles (26,700 kilometers) total, based on data retrieved from his geolocator. The map shows the route and timing of his migration, which included going to the Canadian Arctic for the breeding season and spending his “winter” in Patagonia, Argentina./Courtesy of Larry Niles. (Click the image for larger view.)
In addition to non-stop intercontinental flights of up to eight days, the researchers learned that the birds sometimes make extensive detours around tropical storms during their southbound migration and discovered new migratory paths. Such information will help ongoing conservation efforts for this threatened bird.
“Red Knots have faced terrible population declines in the past ten years,” says Dr. Charles Duncan, Director of the Shorebird Recovery Project at the Manomet Center for Conservation Sciences. “The combination of new technologies in this exciting research with intensive conservation efforts makes us hopeful that, together, we can recover the populations of this amazing bird, one of the planet’s great travelers.”
In May 2009, geolocators were attached to the legs of 47 Red Knots that had been captured during their annual stopover on the Delaware Bay, where they “refuel” on horseshoe crab eggs prior to their final flights to their Canadian Arctic breeding grounds. Three of those birds were recaptured during their return to the Delaware Bay in May 2010, and their geolocators were retrieved. Analyzing the year-long geolocator data, the researchers found that the bird that flew nearly 5,000 miles non-stop for six days also covered one of the longest recorded distances in a year of any bird species: 16,600 miles (26,700 kilometers).
The sunrise- and sunset-sensitive geolocator on this Red Knot’s leg records day-length wherever the bird goes during its annual migration cycle. Researchers then analyze these data recordings to track its journey. © Jan van de Kam
Researchers demonstrated that the lightweight geolocators, seen here in detail, did not affect the Red Knots’ behavior or survival rates. © Jan van de Kam
“We’ve long known that reaching the Arctic in time for breeding requires long-distance northbound flights, thereby making quality stopovers, such as the Delaware Bay, critical for resting and refueling,” says Niles, the project’s chief investigator. “The surprise here was that after the breeding season all three birds with geolocators also made long-distance return flights, highlighting the importance of southbound stopover sites such as Cape Cod in Massachusetts, and New Jersey’s Atlantic coast.”
The data also revealed that during the 2009 southbound migration, tropical storms caused two of the birds to make long, energy-depleting detours. One bird detoured more than 620 miles (1,000 kilometers) to avoid Tropical Storm Danny in late August, and then in early September encountered Tropical Storm Erica before arriving in Brazil. The other bird detoured approximately 870 miles (1,400 kilometers) to avoid strong adverse winds while over the Atlantic before resuming its flight south.
“Global warming models suggest increases in the frequency and strength of tropical storms,” says Niles. “If this happens it could be devastating to shorebirds’ southward migration.”
The study also found that the birds, which most likely were flying as part of a flock, took some previously unknown migratory paths. One bird flew straight across the Amazon, through habitat mostly inhospitable to shorebirds. The data not only re-validated the importance of a number of key, known stopovers (San Antonio Oeste in Argentina, the Maranhão region of northern Brazil, and the Delaware Bay in the U.S.), they also identified a number of previously little-known stopovers, such as the Churchill region of Hudson Bay and the Lesser Antilles in the Caribbean.
Biologist Patricia González is an Argentine researcher who follows the knots to many places along their migratory route. “There are no borders for these birds,” she says. “This kind of project is only possible thanks to the enthusiastic network of researchers, volunteers, and communities that is being built throughout the American flyway. The knots are teaching us about collaboration.”
These results suggest that geolocators are likely to afford valuable new insights to our understanding of Red Knot migration strategies, as well as their breeding and wintering locations. Between May 2009 and May 2010, the research team fitted geolocators to 200 more Red Knots they caught in Canada, Massachusetts, New Jersey, Florida, Texas, and Argentina. The future recovery of some of these birds and their geolocator data will add even more knowledge to aid Red Knot conse
For more information or a copy of the report in the Wader Study Group Bulletin, Vol. 117(2), please contact Dr. Larry Niles at firstname.lastname@example.org.