Red knots are elite athletes of the bird world and stop briefly in Delaware Bay in the spring when horseshoe crabs lay eggs, a spectacle that draws birders and researchers. Seated, from left, are Graham Austin, of the British Trust for Ornithology, Feo Pitcairn, an independent nature photographer and filmmaker, and Michael Parr, of the American Bird Conservancy, survey the birds. Andre Chung/Tribune News Service

The grand spectacle of the fall migration continues. There’s nothing like going out into the field to see the migrants and wish them farewell until the spring. But it’s fun to read about migration as well to gain a broader perspective on the phenomenon.

My favorite book on migration has been Scott Weidensaul’s volume – “Living on the Wind: Across the Hemisphere with Migratory Birds” – published in 2000. Weidensaul describes amazing example after example of migratory feats in his graceful, clear prose.

Bird migration is a popular research topic and our understanding has advanced greatly in the past 20 years. To review this new knowledge, Weidensaul has just published a new book, “A World on the Wing: The Global Odyssey of Migratory Birds.”

This new book is intended to complement rather than replace his 2000 volume. “A World on the Wing” is a series of chapters detailing the author’s own experience with current research. Some of the chapters are devoted to studies in which he is a collaborator and others in which he visits sites to meet with the local researchers. In 10 chapters, we gain insight into new techniques and new findings from around the world.

I expect most readers will have the same envy I do in reading about these fantastic migrations. Weidensaul takes us to China, Alaska, California, Argentina, northwest India, Cyprus and more extralimital areas – as well as more familiar sites in the northeastern United States.

Conservation is a strong thread, tying together all the chapters. Significant and even dire threats imperil migrants in some places. There are some conservation successes that will brighten your day and give hope that threats to other migrants can be mitigated or eliminated.

Red knots descend on Delaware Bay in the spring when horseshoe crabs lay eggs and feast until they’ve doubled their weight, then resume their flight to the Arctic to breed young of their own. Andre Chung/Tribune News Service

We are familiar with the migratory paths of many of the shorebirds that breed in the North American arctic. We know we can see massive numbers of red knots in Delaware Bay in late May and hordes of semipalmated sandpipers in the upper Bay of Fundy in August and September. These birds overwinter in Argentina and Suriname, respectively.

Weidensaul describes conservation challenges for shorebirds wintering in the Pacific Ocean. This flyway, the East Asian-Australasian Flyway, is used by an estimated 8 million shorebirds each year.

This region has roughly the shape of an hourglass. The upper part of the hourglass where these shorebirds nest extends from Alaska westward to include the eastern half of Russia. Most of the shorebirds nest on the arctic tundra.

The lower part of the hourglass, the wintering areas of these shorebirds, includes Indonesia, Australia and New Zealand.

But the narrow center of the hourglass is the Yellow Sea along the Chinese coast. During migrations, Yellow Sea mudflats are stop-over areas for many of the migrant shorebirds, including the endangered spoon-billed sandpiper. Only about 600 spoon-bills exist.

As you can imagine, development pressure is huge along this bottleneck of the Yellow Sea. Weidensaul takes us there and describes the efforts to conserve the Yellow Sea mudflats.

Recent gains in our understanding bird migration stem in part from technologies that were not available 20 years ago when “Living on the Wind” appeared. Satellite transmitters have been miniaturized so small birds can be fitted with these tracking devices.

Geolocators are tiny devices that track the light level every few seconds. The time between dawn and dusk provides the latitude of a fitted bird each day and the mid-time between dawn and dusk provides the longitude. The birds have to be recaptured to download the data but since many birds are faithful to nesting sites, recovery of the data often occurs.

Individual birds can now be tracked on weather radars. Check out birdcast.info to see the power of this approach.

In 2002, the Cornell Lab of Ornithology and the National Audubon launched eBird, a data repository where birders can record and share their sightings. The database is now approaching a billion records!

You’ll learn about more of these new ways of monitoring migration and many of the surprising results.

Herb Wilson taught ornithology and other biology courses at Colby College. He welcomes reader comments and questions at [email protected]


Only subscribers are eligible to post comments. Please subscribe or to participate in the conversation. Here’s why.

Use the form below to reset your password. When you've submitted your account email, we will send an email with a reset code.