Photo by Lou Reuter
 
Photo by Lou Reuter
Birds, such as the yellow warbler and the barn swallow have been migrating for millennia. What triggers them to leave each spring? They are primarily triggered to head north by the length of days. How they navigate northward depends on the species.
 
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Every spring for the past 34 years, Elizabethtown resident Mike Peterson has spent most of May banding birds on the tip of Crown Point on Lake Champlain. That experience has allowed him to learn the habits of many of migratory birds better than most other people.

Among the birds Peterson banded was a little female yellow warbler. This small bird is typically about five inches in length with a wingspan of about eight inches. It weighs but a few ounces. Yet for every year of her life, she engaged in a trip that spanned thousands of miles as she travelled from her wintering grounds in the warmer climates of Central America to the cooler confines of the Adirondack region, where she bred during the warmer months.

“It’s amazing to me that she could come back year after year and not just find the state of New York or Essex County, or the town of Crown Point, but she could find the exact thicket the year before out there at the tip of Crown Point peninsula,” said Peterson, author of “The History of Ornithology and Birding in New York State” and numerous other publications. “I used to be a jet pilot in the Air Force, and that’s pretty good navigation.”

The last time Peterson saw the bird, she was nearly 9 years old.

Every spring, birds such as this yellow warbler travel thousands of miles to breed in the North Country. Some wood warblers and swallows actually travel from the tip of Argentina to get here.

Some, like the Bicknell’s thrush, are very particular about where they go. Bicknell’s thrushes stick to Cuba, Dominican Republic, Jamaica and Puerto Rico in the winter.

In the summer, they are found high on mountain peaks in southeastern Quebec, northern New England, Nova Scotia, the Catskills and the Adirondacks.

Birds arrive as early as March and as late as July. This year, Peterson recorded a wood duck and an eastern bluebird on March 20 and a tree swallow on March 26. Warblers arrive in April, and hummingbirds often arrive in early May.

Moving north

Birds have been migrating for millennia. What lures them to leave each spring? They are primarily triggered to head north by the length of days, Peterson said.

How they navigate northward depends on the species. Some, like sailors, use the sky’s lights.

“They use the sun, and because a lot of them fly by night, they use the stars and the moon,” Peterson said.

There are some theories that some birds, like whales, can detect low-frequency sounds hundreds or thousands of miles away.

“When they are flying high above the earth, a couple miles up, they could conceivably hear the waves breaking out the Atlantic out their right ear when they are coming north and the waves breaking in the Pacific out their left ear,” Peterson said. “Whales can hear low-frequency sounds hundreds, maybe a thousand miles underwater. There’s no reason a bird couldn’t do it high above the earth.”

Birds take different routes, depending on their age, species and gender. Some head up the coast; others travel more inland.

For some birds, a key stop is Sanibel Island, off the coast of Florida on the Gulf of Mexico. Birder Gary Lee, who both banded birds and written books with Peterson, has traveled to this island in the past and witnessed birds as they arrived.

“Lots of times, you get those wood warblers that you see up here around Sanibel, and they just make it across the ocean,” Lee said. “They lay on the beach like they are going to take their last breath.”

One time, Lee said he saw thousands of swallows shortly after they arrived.

“There were over 3,000 or 4,000 swallows in this guy’s yard, and they were sitting on the grass, sitting on his walk, just pooped,” Lee said. “They were just picking cluster flies off his garage door. But they were pooped. They had just made it across the ocean, and they’d had a north wind. They were fighting north wind, and they made it across.”

On the Doppler

Not all birders are able to go south to see birds along their migratory routes, but that doesn’t mean they can’t track them. The Internet has given birders a whole new method of finding birds prior to their arrival here.

“My favorite site, in March, is a Doppler radar site in Key West, Fla.,” said Brian McAllister, who helps organize the Great Adirondack Birding Celebration at the Visitor Interpretive Center in Paul Smiths every summer. “What it’s showing is movements of birds coming off of Cuba. They are all coming up from Central America.”

The birds show up on the radar as a collection of dots, like a storm, moving up the coast.

Other sites such as birdingonthe.net have forums where birders from across North America post bird sightings.

“The Internet just opened up a whole new avenue in the birdwatching world,” McAllister said.

Arriving up north

Once the birds arrive in the Adirondacks, they make their way to their favorite habitats, whether it’s a bog dotted with tamarack trees and pitcher plants or a dense spruce-fir forest high in the mountains.

“They love the conifer forest because they are filled with insects,” McAllister said. “That’s really the main reason birds migrate. They come up to breed in these areas because there is a really good food source here. We’ve got tons of caterpillars in the conifer trees. The denseness of the conifer trees is really thick, protective habitat for them.”

When they are here, they get to their prime objective — mating. It’s not necessarily easy. To get here, these birds travel thousands of miles, sometimes battling coastal storms, hurricanes and predators, to name just a few of the obstacles.

“It’s a tough life, but if you think of it this way, the job of a pair is to replace themselves in their own lifetime,” Peterson said. “They only have to have two of their kids, two of their young survive to adulthood, and they’ve done what they’ve had to do.”

Then those young birds, born here in the Adirondacks, have to make that long migration down to Central America or the Caribbean at just a few months of age. And then come back.