Integrative and Comparative Biology Advance Access originally published online on June 19, 2007
Integrative and Comparative Biology 2007 47(5):786-787; doi:10.1093/icb/icm005
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Book Review |
Handbook of Avian Hybrids of the World. Eugene M. McCarthy.
U.S. Forest Service
Center for Bottomland Hardwoods Research
Handbook of Avian Hybrids of the World.Eugene M. McCarthy. New York, NY: Oxford University Press; 2006. 583 pp. ISBN 0-19-518323-1, $89.50.
Wow, what a great book! Discretion suggests I stop at that first impression, yet the task of reviewing demands that readers receive more for their interest. Eugene McCarthy, a geneticist interested in hybridization, provides more, too, in this extensive documentation of the literature of avian hybridization. His intent was "to provide basic information about each of the thousands of types of reported avian crosses, to provide access to documenting literature, and to familiarize readers with the nature of avian hybridization." I give him extremely high marks for achievement of the second goal, high marks for the first, and a better than passing grade for the third. The work is well organized, with 299 pages devoted to cross-referenced accounts of individual summaries of reported hybrids, 157 pages to a bibliography of more than 5000 citations of hybrids, and a 69-page index of common and scientific names conforming to the usage of Sibley and Monroe (1990). The introduction, at 38 pages, is just that, a brief review of the concepts of hybridization, followed by his rationale for, and organization of, the work. Three short appendices complete the book. That dealing with Canary hybrids runs to more than 70 crosses, including two which are considered dubious based on McCarthy's meticulous evaluation of the original accounts.
The great strength of this book lies in the careful and extensive presentation of the accounts, which are organized alphabetically by species within genus within family. Families are presented in the order of Sibley and Monroe (1990), an older scheme than those presently in use. Given that the work required many years to compile, it is forgivable that more modern sequences were not employed. McCarthy devised a very compact scheme of codes to present the information, which, after minimal reference to the inside front cover where the scheme is presented, was both logical and easy to follow. I salute him for that, and hope that in future editions this scheme will be presented with the code letters capitalized rather than italicized. The scheme includes information about the nature (captive or natural), extent (extensive or not), and quality of information (reported or inferred) about hybridization. Seven categories identify the extent of fertility of hybrids from exceptionally high to very low fertility, variation between sexes in fertility, as well as the viability of hybrids. Additional categories clarify the relationship of breeding ranges in nature. For biologists interested in hybridization, for conservationists interested in particular species, for ornithologists interested in specific relationships, and for birdwatchers intent on evaluating plumages, this book is a goldmine.
We are fortunate that McCarthy takes an inclusive view of hybridization. I am no geneticist, and so am able only to provide rudimentary comment on the notion of hybridization as it is reflected in this treatment. The incredible number of hybrids in certain groups, such as the waterfowl, chicken-like birds, and hummingbirds, leads me to wonder just how useful are specific epithets in these groups. Some readers will no doubt wonder whether this is a work about interspecific hybridization between strictly defined biological species, or a careful documentation of observable phenotypes and variation among them. If the former, then it is clear that speciation is a dynamic, perhaps reversible, reticulate process in birds. If the latter, our nomenclature for species of birds reflects taxa that are surely overly split one from the other. Because pre-zygotic isolating mechanisms in birds are largely behavioral and not morphological, opportunities for hybridization are abundant, much more so than in another group such as insects where morphological geometry precludes copulation. This work is an authoritative resource of cases available for the study of post-zygotic isolating mechanisms between phenotypically distinct populations, including evaluation of those factors associated with the breakdown of pre-zygotic isolating mechanisms in nature.
What is abundantly clear is that this book is a valuable resource. One case in which I have some experience involves hybridization between the Cerulean Warbler (Dendroica cerulea) and other warblers. The materials presented in this book were exhaustive in this respect. The references were sufficient for me to evaluate a particular case of a putative hybrid between D. cerulea and the Northern Parula (Parula americana). My evaluation is that the bird in question was probably a Northern Parula which had failed to produce the yellow color typical of the species, and was thus a leucistic individual rather than a hybrid with a Cerulean Warbler. Readers will find opportunity to evaluate this and many other reports.
Serious bird students have here a tool to help in the identification of peculiar or unfamiliar plumages, though perhaps this book heralds that the number of possible "species" available to be added to one's personal list is subject to reevaluation. The material in this book is indispensable to such examination.
Nowhere in this valuable resource is it indicated that the material included in this hardback volume is available in some electronic format. Ultimately this will become a more valuable resource when it is so presented. As it stands, no university or reference library can afford not to include it in their collection.
Sibley CG, Monroe BL. 1990. Distribution and taxonomy of birds of the world. New Haven: Yale University Press.
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