McCarthy, Handbook of Avian Hybrids of the World
ByWe birders like to think of ourselves as a relatively genteel lot, and most of us can curb our tongue at least in the presence of strangers and the young. But occasionally verbal self-control gives way, and in moments of extreme stress an epithet may be unleashed to the air. “Shoulda been here five minutes ago.” And to the shock of those standing around us, it just slips out. The H-word.
Hybrids are certainly more common than most birders assume. Any close study of a large flock of American Black Ducks, for example, is likely to turn up a green-tinged head here, a bright white secondary tip or tail feather there; leisurely examination of hummingbirds here in southeast Arizona, too, often reveals odd characters most easily explained as miscegenation (see the apparent Violet-crowned x Broad-billed Hummingbird currently delighting visitors to Boyce Thompson Arboretum). And those are just the hybrids we see: in the field, it can be impossible to detect, or to rule out, a hybrid between such closely similar taxa as, say, the meadowlarks or the scaup.
Eugene M. McCarthy, a geneticist at the University of Georgia, has undertaken the herculean–perhaps even sisyphean–task of cataloguing all (all!) known avian crosses. Assembling records from the scientific literature, internet discussions, and personal communications, the Handbook presents telegraphic descriptions and citations to records of many thousands of hybrid combinations; it includes both wild crosses and the products of avicultural experiments and accidents, with a separate appendix devoted entirely to hybrids of the domestic Canary.
Obviously, there is a tremendous amount of information packed into the nearly 600 pages of this volume, and its organization must have been no less a task than its compilation. Happily, McCarthy (and the apparently unmentioned editors and designers at OUP) have devised a clear and simple layout that makes it easy to determine whether a given cross is attested, where and how often it has been recorded, and where in the published literature it is described and discussed.
The individual accounts are presented taxonomically by family, using the Sibley and Monroe sequence, and then, within families, alphabetically by genus and species; English species names are provided in brackets and listed in the index. Duplication is avoided by listing details only under the name of the hybrid partner with alphabetical priority: thus, the full account of hybridization between Violet-crowned and Broad-billed Hummingbirds in Sonora is given at the former species(Amazilia), with a cross-reference at the latter (Cynanthus). The accounts bristle with abbreviations and symbols, and can be at first glance a bit intimidating, but clear definitions are provided on the front endpapers, and the habitual user, or the fascinated browser, will quickly learn what the most frequently encountered mean; with a nod to failing memory, I have photocopied the decodings for use as a bookmark. Our Sonoran hybrid hummer, for example, is described as “NHR,” a naturally occurring hybrid, and the “BRO,” the breeding-range overlap of the presumed parent species, is briefly outlined. A single concise sentence informs us that this combination was originally described as a separate species Amazilia [Cyanomia] salvini; both of those Latin names and the English moniker “Salvin’s Hummingbird” are listed in the index. Eight literature citations direct the interested reader to the Handbook’s 160 pages of bibliography. That’s a lot of information in less than 2 column-inches of text.
For the birder, the most interesting accounts may well be those involving taxa whose species status is unclear. Though McCarthy proclaims in his introduction “the policy … to steer a neutral course on such issues,” he does, sensibly and appropriately, offer his well-formed opinion in a number of cases. Fuertes’s Oriole (its name regrettably misspelled, in one of remarkably few typos I have run across), for example, treated in the current AOU Check-list as a subspecies of Orchard Oriole, is listed here as if a full species, and its relationship to Orchard Oriole sensu stricto is described in a brief and informative summary of Baker et al.’s work on the group. Birders curious about such nonce species as Cooper’s Sandpiper or Townsend’s Bunting will also find McCarthy’s discussions of taxa “described on the basis of one or a few specimens” later determined to be hybrids very welcome, though I was sorry to find no entry for Alfaro’s Hummingbird.
The hybrid accounts are preceded by a 35-page introduction. While the first pages introduce the reader to using the book, most of this extremely useful section is dedicated to a general discussion of the phenomenon of avian hybridization and the ideas and problems central to its study. Birders will find especially valuable the sections “Identifying Hybrids” and “Expression of Parental Traits in Hybrids,” but will profit greatly from a careful reading of the entire introduction.
Many of us, I think, will discover that the Handbook offers not just profit but the pleasure of surprise. Who would have guessed that Mourning Doves and Rock Pigeons could be crossed in captivity, or that an obviously desperate Florida Scrub-Jay raised young with a Blue Jay? The waterfowl section, of course, offers a prurient glimpse into an avian Peyton Place, and for horror fans, even the reminder that Chihuahuan and Common Ravens hybridize “extensively” in the American southwest provides a bit of masochistic entertainment.
The Handbook of Avian Hybrids is an impressive accomplishment, one that can be equally savored by browsing birders and appreciated by serious students of one of the biggest birding challenges out there. Highly recommended.
