Gyrfalcon, The

Auk, The, Jul 2006 by Cade, Tom J

The Gyrfalcon.-Eugene Potapov and Richard Sale. 2005. Yale University Press, New Haven, Connecticut. 288 pp. ISBN 0-300-10778-1. Cloth, $45.-Latest in what has been a distinguished Poyser series of monographs on birds of prey, this book is mainly a descriptive biology of the Gyrfalcon (Falco rusticolus)-the largest of falcons, circumpolar in distribution, and with unique adaptations to life in harsh Arctic environments. The first nine chapters treat paleobiography and systematics; identification and colors; distribution; population; habitat and landscape preferences; food and feeding habits; breeding cycle; dispersal, seasonal movements, and winter distribution; and competitors, commensals, and conspecifics. The final two chapters deal with man and falcons and threats and conservation.

Because neither author has done much original research on the Gyrfalcon, their book is mainly a review of the literature, though they present original research on morphometrics and plumage variations based on extensive examination of museum skins. By far the most important contribution of this book is its comprehensive summary of the Russian literature on the Gyrfalcon, much of which occurs in rather obscure sources. Being Russian, with a developing ability to communicate in English, Potapov is qualified to bridge the two languages, but he needed more help than he evidently got from his editors and coauthor in smoothing out rough passages of text. Even so, it is exciting to read details about the natural history of the Gyrfalcon from the first-hand accounts of Russian field workers searching out the vast expanses of the Russian and Siberian northlands for this rare falcon. The ~500 references include no fewer than 162 Russian titles (translated). Finnish and Scandinavian languages are also well represented and, overall, the list of titles is a rich compendium of the world literature on the Gyrfalcon.

Unfortunately, the book was not well edited and contains many errors-omission of words, tandem duplication of the same word, misspellings (including authors' names and scientific names), and confusions resulting from poor use of English. The legends for some figures and plates lack sufficient information to allow the reader to interpret what the depicted data are supposed to represent (see especially figs. 2.1, 2.2, and 2.3 and plates 3-7 dealing with plumage color and pattern). In all, I found more than 260 errors and confusions in 280 pages of text and references. Clearly, the manuscript for this book needed meticulous copyediting, which it did not receive.

Chapter 1, with Olga Potapova as senior author, presents an interesting paleogeographic theory to explain how the proto-Gyrfalcon population became geographically isolated from the ancestral Saker (F. cherrug) or Saker-Gyrfalcon common ancestor as a result of an uninhabitable barrier of larch forest that spread across Eurasia, separating the northern tundra grasslands from the southern steppes, starting around 9,000 BP. One problem with this explanation is whether or not the genetic and phenotypic differentiations between Gyrfalcons and Sakers could have taken place in less than 10,000 years BP. Wink et al. (2004) estimated-from interspecific genetic distances ranging from 0.4% to 2.0% among falcon species in the Hierofalco group, which includes the Saker and Gyrfalcon-that this amount of differentiation would have occurred in a period of 200,000-1,000,000 years BP. They further pointed out that among other bird families, such small genetic distances indicate taxonomic differentiation at no more than the level of subspecies. In that regard, as Potapova et al. point out, the Gyrfalcon and Saker breeding populations remain totally allopatric, unless the much-discussed "Altai Falcon" in the mountains of central Asia represents a hybridized population of the two forms. Also, in captivity the two forms are fully fertile at least through the F^sub 3^ to F^sub 4^ generations, which indicates an absence of reproductive isolating mechanisms. The accumulating data point to the likelihood that the Gyrfalcon and Saker are allopatric populations of the same species (Cade et al. 1998); even so, it is difficult to understand how the differences between them could have accumulated in less than 10,000 years. Work on other groups of avian species involving estimates of species divergence times based on molecular systematics and "clocks" indicate that most recent species divergence events occurred from 1 to 5 million years ago and that late Pleistocene isolations caused by glaciation and associated climate-induced changes in biomes occurred too recently to account for speciation events (Klicka and Zink 1997).

Ever since publication of the 10th edition of Systema Naturae (Linnaeus 1758), argument has raged over the correct binomial for the Gyrfalcon (Hartert 1915, Lönnberg 1931, Dementiev 1960, Banks and Browning 1995). At least since the 11th century, the Gyrfalcon was known in Latin treatises on natural history and falconry as girofalco or gyrofalco (and other variations), and in his 10th edition, Linnaeus (1758) described a bird of prey under the name Falco gyrfalco. His verbal description is marginally adequate to fit the Gyrfalcon, but he also referred to a picture of a Northern Goshawk (Accipiter gentilis) published under the name F. gyrfalco in his earlier work, Fauna Svecica (1746), thereby invalidating the use of this name for the Gyrfalcon, according to Lönnberg (1931). A name having page priority (first use) in the 10th edition (Linnaeus 1758) is F. rusticolus, but the diagnosis accompanying this name is less clearly referable to the Gyrfalcon than that of F. gyrfalco and should be rejected as a nomen dubium according to Potapov and Sale. Hartert (1915), the de facto "first reviser" of the Gyrfalcon's nomenclature (not Lönnberg [1931], as the authors state), became convinced that rusticolus is the correct name, and it is the one that has been in most general use in the post-Linnaean period, except in Russia, where several authorities, notably Peter Pallas and G. P. Dementiev, continued to use gyrfalco. Potapov and Sale lead us through the modernized but still byzantine International Code of Zoological Nomenclature (4th edition, 1999) in an effort to prove that the Russians are right. One hopes their arguments are convincing and that the International Commission will one day validate the historical and most apposite name, Falco gyrfalco.