The great spectacle of the fall migration continues. Nothing like going out into the field to see the migrants and wish them goodbye until spring. But it’s also fun to read about migration to get a broader perspective on the phenomenon.
My favorite book on migration is Scott Weidensaul’s volume – “Living on the Wind: Across the Hemisphere with Migrating Birds” – published in 2000. Weidensaul describes example after example of migratory feats in his graceful and clear prose.
Bird migration is a popular research topic, and our understanding has grown considerably over the past 20 years. To take stock of 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 its 2000 volume. “A World on the Wing” is a series of chapters detailing the author’s own experience with current research. Some chapters are devoted to studies in which he is a collaborator and others where he visits sites to meet local researchers. In 10 chapters, we discover new techniques and new discoveries from all over the world.
I expect most readers to have the same urge as I am reading these fantastic migrations. Weidensaul takes us to China, Alaska, California, Argentina, northwest India, Cyprus and more extra-border regions – as well as more familiar sites in the northeastern United States. .
Conservation is a common thread that links all the chapters. Significant, if not terrible, threats put migrants at risk in some places. Some conservation successes will brighten your day and give hope that threats to other migrants can be mitigated or eliminated.
We know the migratory routes of many shorebirds that breed in the North American Arctic. We know we can see massive numbers of Red Knot in Delaware Bay in late May and hordes of Semipalmated Sandpipers in the upper Bay of Fundy in August and September. These birds winter in Argentina and Suriname respectively.
Weidensaul describes the conservation challenges for shorebirds wintering in the Pacific Ocean. This flyway, the East Asian-Australasian Flyway, is used by approximately 8 million shorebirds each year.
This region is roughly shaped like an hourglass. The upper part of the hourglass where these shorebirds nest stretches from Alaska westward to include the eastern half of Russia. Most shorebirds nest in the arctic tundra.
The lower hourglass, the wintering grounds for 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, the mudflats of the Yellow Sea are staging areas for many migratory shorebirds, including the endangered Spoonbill. There are only about 600 spatulas.
As you can imagine, development pressure is enormous along this Yellow Sea bottleneck. Weidensaul takes us there and describes the efforts to conserve the mudflats of the Yellow Sea.
Recent advances in our understanding of bird migration come in part from technologies that were not available 20 years ago when “Living on the Wind” first appeared. Satellite transmitters have been miniaturized so that small birds can be fitted with these tracking devices.
Geolocators are tiny devices that track the level of light every few seconds. The time between dawn and dusk provides a bird’s latitude adjusted each day and the time between dawn and dusk provides the longitude. Birds must be recaptured to download the data, but since many birds are loyal to nesting sites, data retrieval 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 one billion records!
You will learn about these new methods of migration monitoring and many of the surprising results.
Herb Wilson has taught ornithology and other biology courses at Colby College. It welcomes comments and questions from readers on [email protected]
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