Gatherings of Angels: Migrating Birds and Their Ecology.—Kenneth P. Able [ed.]. 1999. Cornell University Press, Ithaca, NY. xi + 193 pp., 52 color plates, 36 text figures. ISBN 0-8014-3362-2. $29.95 (cloth).
With the current profusion of media featuring migratory birds, it may seem superfluous to release a new volume entirely devoted to introducing a general audience to the marvelous phenomenon of bird migration. However, from the opening chapter of Gatherings of Angels, it is easy to appreciate the almost empty niche that this volume will fill. In easy to understand language, Kenneth P. Able and a select group of co-authors manage to provide a broad coverage of the major ecological problems faced by a wide variety of migratory species in their annual pilgrimage across the two continents of the Western Hemisphere.
In the first two chapters, Able sets the framework for topics that will be addressed in the rest of the book. The reader is gradually introduced to the complexity of migratory movements, from some basic definitions to specific issues, such as evolution of migration, physiological aspects of the annual cycle, timing and its relation to weather, and orientation. Thanks to the clarity and comprehensiveness of those chapters, any interested person with no previous knowledge of migration can easily read the rest of the book.
In the third chapter, Sydney A. Gauthreaux renders an interesting summary of passerine trans-gulf migration. Even though this account will undoubtedly contribute to a better appreciation by the general public of the magnitude of risks faced by North American migratory songbirds every year, the technicality of several figures makes them difficult to interpret for a layperson. Also, the detail of the historic account of the trans-gulf migration is excessive, and does not add much to the point at hand. Frank R. Moore explores this issue further in the fourth chapter in a brief but eloquent account. An apparently local problem is presented in its real context: the necessity of preserving the coastal woodlands of Louisiana because of their critical role as stopover sites during spring migration.
The bulk of the book is composed of a series of chapters dealing with migration of particular species. In general, the authors make colorful and interesting accounts that build upon the main issues addressed in the introductory chapters. James Baird's coverage of migration of Blackpoll Warbler (Dendroica striata) over the eastern Atlantic Ocean is perhaps the most interesting for the general public, both for its balanced treatment of speculative information and for conveying the marvel of such a long non-stop flight by this small songbird, and without losing scientific rigor.
The annual cycle of the Broad-winged Hawk (Buteo platypterus) described by Keith L. Bildstein is also fascinating. Besides presenting the complex issue of a migratory movement that depends on the availability of thermal currents, the author gives an interesting overview of the passage of several other raptors over Hawk Mountain in Pennsylvania, and a historic account of this important sanctuary.
The description of movements of Sandhill Cranes (Grus canadensis) along the Platte River in Nebraska made by Gary L. Krapu seems to me a little too specific for a general audience. Even though the issue of how human-induced landscape transformation may affect migratory populations is clear, details of such changes in the Platte River overweigh the information on cranes, which is the subject more appealing to readers.
Brian Harrington's chapter on White-rumped Sandpiper (Calidris fuscicollis), and Stanley E. Senner's on Dunlin (C. alpina) and Western Sandpiper (C. mauri), follow the migratory routes of those shorebirds, identifying factors critical to their continued forays across the entire Western Hemisphere. The use of sound scientific information by both authors is made in easy-to-follow language, and even though they address subjects widely publicized in recent years, the phenomenon of the migration of those small “peeps” will undoubtedly attract new supporting fans thanks to those chapters.
The last chapter is William Calder's account on the passage of migrating hummingbirds through the Rocky Mountains. In a very readable way, Calder explains how migration of those birds is timed to availability of floral resources along their route, and then speculates on the future of that movement in response to habitat and climate changes. I have no doubt that this chapter will be one of the most interesting ones for readers, because it features some migratory species less known by the general public.
The epilogue by Kenneth P. Able is an adequate closing to this remarkable selection of writings by some of the foremost researchers on bird migration in the Americas. In a very balanced treatment, Able summarizes the main causes of decline of Neotropical migrants, and introduces the reader to the problems faced by conservationists in their quest to preserve them. Any reader who gets to the last pages of the book will surely be added to the increasing crowd of supporters to this cause. As such, I believe that this book belongs in the library of anyone interested in bird migration.—