Gatherings of Angels: Migrating Birds and Their Ecology

Migration is perhaps the most interesting behavior that birds exhibit. At least it is to me. In this book Kenneth Able brings together works from others to present an interesting examination of bird migration. Eight authors have provided chapters on topics or migratory birds that they are expertly familiar with, preceded by two chapters from the editor giving a general overview of migration.

Background

The first two chapters were written by the editor to give an overview of migration in general – the how, when, where, and why. They are basically a primer, giving the background information necessary to understand the following material. Here he defines the various types of migration, touches on how it may have evolved, and explains how birds can navigate the astounding distances that they travel. Able gives an adequate summary for the purposes of this book. You will definitely want to read these chapters first before tackling any of the others unless you have a very good general grasp on migration. However, 25 pages is not nearly enough room to truly do the subject justice. In the likely case that this brief synopsis whets your appetite to learn more about these things then you will need to find your fill elsewhere (some suggestions to follow).

The Gulf of Mexico

Chapters three and four focus on migrants and the Gulf of Mexico. Birders today are well aware that neotropical migrants wintering in Central or South America and breeding in eastern North America have a couple of options available to travel back-and-forth. They can skirt around the Gulf of Mexico along the coast of Mexico and Texas, or via the Caribbean islands and Florida, in what is known as “circum-Gulf migration”. Or they can take the direct route and fly straight over the gulf (“trans-Gulf”). In the first of these chapters Sidney Gauthreaux describes both of these strategies. He reminds us that the idea of trans-Gulf migration has been highly controversial and was not entirely settled until relatively recently. The best evidence for this phenomenon was provided by an unlikely source – weather radar. It was discovered that the radar was actually detecting flocks of migrating birds in the echoes that radar operators called “angels” (from which this book gets its title). Gauthreaux goes on to discuss the evolution, characteristics, and timing of this migration.

Frank Moore then discusses what the migrants do in the spring once they make it across the Gulf, focusing on the cheniers of Louisiana. These are isolated forested habitats along slight rises of the ground in the marsh and prairie of coastal Louisiana. Moore describes the migrants’ choices in where to stop, what to eat, and even when to sleep. This chapter provides an interesting glimpse into a very small, but important, aspect of the lives of these birds.

Amazing Migrants

Among the “confusing fall warblers”, perhaps the trickiest to tell apart are the Blackpoll and Bay-breasted. You know it’s bad when birders have coined a term for a bird that was either one or the other – the “Baypoll Warbler”. But birders in the south don’t face this conundrum as much as those further north. It’s not that we’re any better at identifying them; it’s simply that we don’t see very many Blackpolls in the fall. The reason is that their migration path takes them hundreds of miles away, not to the west where you would expect, but to the east over the Atlantic Ocean! In the fifth chapter of this book James Baird describes this amazing performance. The fact that this tiny bird can take off from the upper Atlantic coast and fly nonstop to Venezuela, a distance of 2,200 miles, is almost unbelievable. The account here is a wonderful read, even if you’re already familiar with this trek. The only glaring omission is the answer to the obvious question of “Why?!?” How in the world could this migration strategy have come to be? For a possible answer to that question I highly recommend Scott Weidensaul’s Living on the Wind

Up next is Keith Bildstein’s account of the migration of Broad-winged Hawks. Along with the expected species specific information, general concepts in raptor migration are also introduced. There’s even a brief history and description of Hawk Mountain Sanctuary. This is a fine introduction to raptor migration, but is no more than a cursory glance when compared to the author’s Migrating Raptors of the World (my review). Unless you are specifically interested in the Broad-wings I would suggest skipping this appetizer and proceeding directly to the main course.

Perhaps the most obscure bird featured in this book is the White-rumped Sandpiper, treated here by Brian Harrington. But that obscurity makes it all the more interesting. The writing is both informative and intriguing as Harrington chronicles this shorebird’s migration across the two hemispheres. In fact, it made me want to select the author’s The Flight of the Red Knot as my next book to read.

Some insight into hummingbird migration is offered by William Calder. Calder bands hummingbirds, mostly Rufous and Broad-tailed, every year in the meadows of the Rocky Mountains. He details their behavior during migration and reveals some patterns of their migration routes based on banding and recovery data. However, the small number of recoveries makes this tentative at best. I was also disappointed that more attention wasn’t paid to the increasing number of these birds wintering in the southeastern United States (although I suppose the age of the book could have something to do with that).

Amazing Locations

Among the greatest migration spectacles in the world has to be the gathering of Sandhill Cranes on the Platte River in Nebraska. Here Gary Krapu describes the setting, its history, and his studies to find out why so many cranes gather there and what kind of habitat they need. The results of those studies are very important, because the suitable habitat for cranes along the Platte has been declining due to human activity.

And finally, Stanley Senner takes us to the Copper River Delta along the Alaskan coast, where unfathomable numbers of shorebirds congregate each spring. After studying the birds there he found that this was a stopover point, a staging area where the birds come to rest and (mainly) eat. After a few days at the delta they will move along to their breeding grounds. Through some amazing cooperation with other researchers a string of these stopover locations were identified all along the Pacific coast. This information is extremely significant to conservationists, as these places need to be protected just as much as nesting habitat. After all, when this one location hosts virtually the entire world population of Western Sandpipers its loss would be catastrophic.

 

A common theme in many of these chapters is conservation, so it is appropriate that the editor dedicates the epilogue to this topic. This is an excellent summary of the trials, mostly of human origin, that these birds face.

Additionally, there are 24 pages of color photographs that show some of the birds and places mentioned. Even though the photo sizes are fairly small in order to accommodate as many as possible, they are a welcome inclusion.

The writings contained in this book were uniformly informative, and most of them were a true joy to read. If you’re looking for a general survey on migration, or are interested in any of the specific birds covered, then this book is recommended. However, there are some shortcomings. As you may have noticed, the book focuses on American birds. Most of the concepts can be generalized so as to be applicable to migrants everywhere, but it would have been nice to hear specifically about some birds from different places. Also, while it presents a detailed look at some particular birds, the general topic of migration is very lightly covered. If you want more than a hurried explanation of why and how birds migrate then you will need to look elsewhere, such as in the books listed below.

Further Reading:

• Living on the Wind: Across the Hemisphere With Migratory Birds, by Scott Weidensaul – Highly Recommended!!
• How Birds Migrate, by Paul Kerlinger – I haven’t read this, but have heard good things.
• Migrating Raptors of the World: Their Ecology and Conservation, by Keith L. Bildstein – my review
• The Flight of the Red Knot, by Brian Harrington