Migrating waterbirds over South Dakota’s Huron Wetland Management District on North America’s Central Flyway. Sandra Uecker, USFWS/Flickr
Although it still feels like beach weather across much of North America, billions of birds have started taking wing for one of nature’s great spectacles: fall migration. Birds fly south from the northern U.S. and Canada to wintering grounds in the southern U.S., Caribbean and Latin America, sometimes covering thousands of miles. Other birds leave temperate Eurasia for Africa, tropical Asia or Australia.
Using observation records and data collected through bird banding, 20th-century ornithologists roughly mapped general migration routes and timing for most migratory species. Later, using radar at airports and weather stations, they discovered how weather and other factors affect when birds migrate and how high they fly.
Today, technological advances are providing new insights into bird migration and showing that it is more complex and wonderful than scientists ever imagined. These new and constantly improving technologies are key aids for protecting migratory birds in the face of habitat loss and other threats.
Migratory flyways are paths that birds have traveled for centuries. Scientists are working to better understand how birds use these routes.
Birding across borders
The power of the internet has greatly aided migratory bird research. Using the popular eBird network, birders all over the world can upload sightings to a central database, creating a real-time record of the ebb and flow of migration. Ornithologists have also learned to use NEXRAD, a national network of Doppler weather radars, to visualize birds migrating down the North American continent.
Now, scientists are setting up a global network of receiver stations called the Motus Network, which currently has 1,500 receivers in 31 countries. Each receiver constantly records the presence of any birds or other animals within a nine-mile (15-kilometer) radius that scientists have fitted with small, lightweight radio transmitters, and shares the data online. The network will become increasingly useful for understanding bird migration as more receiver stations become active along migration tracks.
Tracking individual birds via satellite
Three new technologies are rapidly expanding what we know about bird migration. The first is satellite telemetry of bird movement. Researchers fit birds with small solar-powered transmitters, which send data on the birds’ locations to a satellite and then on to a scientist’s office computer. The scientist can learn where a bird is, the route it took to get there and how fast it travels.
For example, the bar-tailed godwit, a pigeon-sized shorebird, breeds in Alaska and then migrates to New Zealand. Satellite transmitters show that godwits often fly nonstop from Alaska to New Zealand. Recently, a godwit set the record for the longest nonstop flight by a land bird: 8,100 miles (13,000 kilometers) in 10 days, from Alaska to Australia.
Bar-tailed godwits have the ability to correct course if they are blown off track on their epic migratory journey.
Satellite telemetry studies show how much individual birds, even those from the same breeding location, vary in their migratory behavior. Individual differences in migratory behavior are probably due to differences in physical condition, learning, experience and personal preferences.
Another shorebird, the whimbrel, also makes a phenomenally long journey over the ocean. Satellite telemetry has shown that some whimbrels travel from northwest Canada, across the North American continent to Canada’s east coast, then set off over the Atlantic Ocean on a 3,400-mile (5,400-kilometer), six-day nonstop flight to the coast of Brazil. […]
Professor of Biology, Clarkson University