While You Were Sleeping

Thousands are flying through the night now. As the dog days of summer hit Connecticut, complete with heat waves full of hot, humid weather, drought, and nights filled with the raucous, sharp, three- or four-syllabled buzzing of the Common Katydid (Pterophylla camellifolia), you might not usually think of birds flying south. But they are.

This is the peak “fall” migration for many shorebirds, who either nested here or are just passing through on their way to wintering grounds in the southern United States, and in Central and South America.

You’ll often see quite a few species in large numbers stop to rest and re-fuel along the coast. I recently checked the CTBirds email list server sponsored by the Connecticut Ornithological Association. Someone had spotted more than 1,000 Common Terns (Sterna hirundo) feeding and resting at Stratford Point in Stratford, Connecticut.

The Prairie Pothole region in the western United States and mudflats along the eastern and western coasts provide critical refueling stops for migrating shorebirds. The birds will fatten up on small fish, crabs, worms, and more. Photo by USFWS Mountain-Prairie, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0&gt;, via Wikimedia Commons.

Other places in the state to see migrating shorebirds include Hammonasset Beach State Park in Madison, Connecticut Audubon Society Coastal Center at Milford Point, Bluff Point State Park and Coastal Reserve in Groton, and more. Check out the book Birding in Connecticut (Wesleyan University Press, Garnet Books, 2018) by Frank Gallo for what species to see where and when.

Most birds migrate during the night. There are several possible reasons for this. These birds are diurnal feeders and it is easier to find food during the day. There are also fewer predators at night. And it is easier for birds to fly at night when the cooler, denser air helps them generate more lift. Birds use the stars to navigate on their journey south. They also use magnetoreception to sense Earth’s magnetic field, which guides them on when and where to stop.

The Cornell Laboratory of Ornithology has a very informative site, the BirdCast Migration Dashboard, that uses radar to show the approximate number and type of birds that migrated the previous night. It gives the direction of travel, general altitude, and speed of the birds. On August 11, 2022, around 202,600 birds crossed through Connecticut. At 1:50 am, the migration peaked at 134,100 birds traveling at an average speed of 26 miles per hour (about 42 kilometers per hour) at a height of 1,500 feet (about 457 meters)!

The shorebirds passing through that night included Least Sandpipers (Calidris minutilla), Short-billed Dowitchers (Limnodromus griseus), Long-billed Dowitchers (Limnodromus scolopaceus), Semipalmated Sandpipers (Calidris pusilla), and Semipalmated Plovers (Charadrius semipalmatus).

A Least Sandpiper in breeding plumage, refueling while migrating north in the spring. Photo by Peterwchen, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0&gt;, via Wikimedia Commons.

The endurance these shorebirds is truly remarkable. Biologists think that the eastern population of the Least Sandpiper, after nesting on the tundra of northern Canada, travels down the Gulf of St. Lawrence and the eastern coast of New England before flying non-stop 1,800 to 2,500 miles (about 550 to 760 kilometers) to northern South America! This bird weighs only an ounce (28 grams) and is only 5 to 6 inches (13 to 15 centimeters) long. It is the smallest shorebird in the world.

Range map of the Least Sandpiper. The summer breeding grounds are in orange, migration or transitional areas in yellow, and winter range in blue. Biologists think the eastern population flies non-stop for the Bay of Fundy and New England coast to northern South America. Image by Cephas, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0&gt;, via Wikimedia Commons.
A Least Sandpiper and chick. Many shorebird species nest on the arctic tundra in northern Canada and Alaska. Photo by U.S. Fish and Wildlife Service, Public domain, via Wikimedia Commons.

Like a jumbo jet, to make such a long, non-stop trip requires lots of fuel. Shorebirds fatten up before their flight. Some species double their weight before leaving. They shed unneeded weight by reducing the size of their leg muscles and digestive system, but gain it back when they arrive. The flight muscles also get larger and their blood thickens, allowing these birds to pump more oxygen through their body.

If you have binoculars, a spotting scope, or a telescope, and it is a night with a full moon or close to one, a fun activity would be to go out to watch the moon for a while. You’ll often see the silhouettes of flocks of birds flying across the moon’s face. The next full moons during this year’s migration will be on September 10 and October 9. I’ll make it a point to stay awake and catch this wonderful autumnal sight—and maybe you can too.

Published by Jim Sirch

Jim Sirch is the author of Beyond Your Back Door, a weekly blog about nature in your neighborhood. He is also Education Coordinator for the Yale Peabody Museum, a UConn Master Gardener and board member of his local land trust. As a trained naturalist, he brings a deep understanding of geology, plants and wildlife and how they interact within a particular ecosystem. He holds a B.S in Forestry from West Virginia University, a B.S. from Miami University in Science Education; and an M.S. in Environmental Studies Administration from Antioch University. He is also the 2014 Sigmund Abeles Award recipient from the Connecticut Science Teachers and Supervisors Association for outstanding science teaching and professional development.

9 thoughts on “While You Were Sleeping

  1. Loved this post, Jim. I hadn’t until today checked out the fabulous migration dashboard. Thanks! Yes, let’s take our binos out on Sept 10 and do some full-moon birdwatching! Best, Christin

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  2. Amazing information. I never thought birds traveled at night and they had so many navigational superpowers. Wow. Thank you!

    Sent from the all new AOL app for Android

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  3. For the past couple years in August and September I have seen quite a few sandpipers in the mud flats of the field across the West River from the duck pond in Edgewood Park. Then they fixed the broken flood control gates (this may not be the right term) down near the mouth of the River, the field dried up, and the mud flats are gone – so almost no sandpipers this year. I think I have seen one spotted sandpiper along the river bank, and one solitary sandpiper (I think) which I have seen a few times foraging among the ducks and geese in the small muddy area near the pond.

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