Coming soon to a sky near you: 500 million birds
On peak migration days, as many as 500 million birds could be flying under cover of darkness across America.
- Spring migrations runs between March 1 and June 15.
- Fall migration runs between August 1 and November 30.
- Peak spring migration is in April.
Birds are on the move as their annual spring migration begins. Radar tracking allows you to follow along to see what birds are flying overhead as the birds move to their summer feeding grounds.
"The movements are massive," said Andrew Farnsworth, a migration ecologist at Cornell University who works with the university's ornithology lab. "On a big night in the spring, you're talking 450 to 500 million birds flying under cover of darkness."
It's a time of year when local birds that went south for the winter return or birds heading farther north stop to feed.
"Right now we're seeing lots of movement in Florida and the Southeastern United States as well as in some midwestern states," Farnsworth said.
“The ruby-crowned kinglet, swamp sparrow and eastern phoebe are starting to migrate. They’ve mostly spent their winter in the southeast and are starting to move north,” he said.
“In areas like Kansas, you’re seeing a lot of waterfowl on the move, along with sparrows,” he said. Species include the fox sparrow, the American tree sparrow and the dark-eyed junco. Also the red-winged blackbird and the common grackle.
Cornell University's Bird lab hosts a BirdCast Migration Dashboard that gives daily summaries of radar-based nocturnal bird migration. With it, you can watch the progress of birds as they waft their way across the nation and even track how many flew over your county the night before.
The system uses radar because most species migrate at night, some at altitudes as high as 15,000 feet, and aren't visible to the naked eye.
When is peak bird migration?
In the contiguous United States, peak spring bird migration runs approximately between March 1 and June 15, though some species migrate earlier or later. Fall migration is generally between Aug. 1 and Nov. 30.
Peak migration is defined by the seasonal window during which about 50% of nighttime bird migration traffic passes through an area. On a map you can see a wave of peak migration move up from the southernmost United States to the far north as temperatures slowly rise over the course of the spring.
The biggest peaks are still to come.
"It's not until April that you really start to get the big bang of bird diversity," he said. "The peak migration comes like a wave across the United States, breaking from south to north."
Who's migrating near you?
BirdCast has live, local bird migration alerts so you can see who's flying through your area at any time.
Numbers are especially high right now in New Mexico, Texas, Oklahoma and somewhat in the Maryland-New Jersey area.
There's also a migration prediction map that shows upcoming nocturnal migrations. For example, the night of March 10 to 11, an estimated 20 million birds were predicted to be migrating in the United States. Areas of high migration include Iowa, central Texas and up into Oklahoma.
That night in Des Moines County, Iowa, an estimated 158,700 birds crossed the county, including snow geese, dark-eyed juncos, killdeers, white-throated sparrows, yellow-bellied sapsuckers, northern shovelers and buffleheads.
Why do birds migrate?
In North America, birds typically fly south for the winter before food is less available during the colder months, then back north in the spring to take advantage of growing insect populations, budding plants and good nesting locations.
Come winter, those same birds will fly south again to escape the cold and find better food sources.
There are five types to look for, with larger birds tending to make longer trips.
◾Permanent residents: These are birds who don't always migrate, sometimes because there's enough food where they live. They can include the the American crow, the common raven, mourning doves, wild turkeys and in Florida many types of herons.
◾Altitudinal migrants: These are birds who change altitude, not location, generally up or down a mountain. Think of the Rocky Mountains and birds such as Clark's nutcracker, the mountain chickadee and rosy finches. Whether higher elevation birds move depends on local conditions.
◾Short-distance migrants: These can include the eastern phoebe, the yellow-bellied sapsucker and the song sparrow.
◾Medium-distance migrants: These are birds that migrate a few hundred miles. They might breed in the Northeastern U.S. and winter in the Southeast. Some breed in the eastern deciduous forests and migrate to Central and South America or the Caribbean. These are often shorebirds. Species include many types of warblers, the western tanager and the snow bunting.
◾Long-distance migrants: These birds fly thousands of miles, often from the northern United States and Canada to wintering grounds in Central and South America, sometimes as far as 8,000 miles. These are often shorebirds, including birds that breed on the tundra and winter in southern South America. Some species include the arctic tern, Hudsonian godwit, long-tailed jaeger and the bobolink. The blackpoll warbler songbird can fly as far from Alaska to the Amazon.
Exactly how birds know where and when to migrate, especially those that have never made the flight before, is still something of a mystery. Research shows that the length of the day, smell, the location of the sun and the stars and even sensing Earth's magnetic field are all involved.
Changes to when plants first bud and insects become available due to a warming planet are wreaking havoc with some species' migration patterns. The mismatch of their migration with food sources puts them out of sync with what's available, leaving them hungry just when they need to eat so they can breed.
To aid birds as they migrate, ornithologists urge Americans to turn off nonessential lighting from 11 p.m. to 6 a.m. during peak migration periods. Bright lights can attract and disorient birds that migrate at night, potentially causing fatal collisions with buildings.
“These simple steps can help protect them,” said Farnsworth. “And please make sure any glass in your house is bird friendly.”