A third shoe has fallen with the publication of Anderson's evaluation of H. C. Hanson's 193 subspecies of white-cheeked geese (i.e., Canada Geese [Branta canadensis]). The first two “shoes” were volumes written by Hanson and principally edited and privately published by Anderson (Hanson 2006, 2008). Hanson, working for the Illinois Natural History Survey and largely supported by the U.S. Fish and Wildlife Service, spent most of his life studying white-cheeked geese and worked toward a better taxonomic understanding that would be of aid in management of this morphologically complex species. A fourth volume is in the offing.
Chapter 1 of the current volume reviews the taxonomic history of white-cheeked geese, although many would question some of the authorities cited, and sets the goal of objectively determining whether a case can be made to support Hanson's major conclusions. Chapter 2 is essentially the methods section, describing the scoring system that Anderson used to quantify plumage color and patterns. For his analysis, Anderson used 16 plumage characters that were assigned values of “1 or =/> 3,” although in table 2.1 where these are defined, they are given values of 1–3, 1–4, 1–5, and 1–8, with intermediate values used if needed for plumage characters. Standard measurements and a series of bill measurements were taken and ratios were used (particularly ratio of toe length to tarsus length—in three of Hanson's species of large geese these were >1.0, whereas in Arctic geese these were <1.0). He proposes six size classes (SC) from 1 (minima) to 6 (maxima). About two-thirds of specimens within a given SC were separable from those of an adjacent SC for any given measurement, and >80% could be distinguished with the use of several measurements. Chapters 3 through 6 discuss size-class variation within age and sex classes, the effects of sample size (a sample of <10 was virtually useless using his methodology), the reproducibility of plumage scores, and the taxonomic value of migrant specimens. He concluded that (contra opinion in the literature) migrants, who often formed the bulk of the specimens of a sample, are highly useful. He demonstrates, with ample statistical support, that current nomenclature does not accurately reflect the morphological variation found among the white-cheeked goose populations—a conclusion that anyone who has tried to identify small geese from small samples collected over several seasons would readily agree with!
In chapter 7, Anderson analyzes variation within and among Hanson's taxa and clinal variation within “Grassland and Rocky Mountain taxa,” “Rocky Mountain and Boreal Forest taxa,” “B. hutchinsoni [groups],” and “B. hutchinsoni: Boreal Forest taxa.” Anderson continues to examine clinal variation among Hanson's B. canadensis complex in chapter 8 and among 39 of the ∼100 taxa that Hanson described in his “arctic-geese” in chapter 9. He concludes that there is no clinal variation among any of the groups (except possibly in size among Arctic populations) and that nearest neighbors are usually not the closest related, opening the possibility that there is more than one evolutionary line within these groups and that these lines intertwine.
Chapters 10 and 11 are the core of this publication. In these chapters Anderson conducts two cluster analyses. In the first he used 2,555 specimens in 71 taxa of “large” geese of the canadensis and maxima complexes recognized by Hanson plus four “potential taxa,” and in the second he used 1,712 specimens of 54 taxa of Hanson's Arctic geese plus two potential taxa. These dendrograms yield nine “stems” of large geese and six “stems” of Arctic geese recognized by Anderson as allospecies. Chapter 12 poses an evolutionary scenario “through the quantitative study of 4,500 specimens.” The small geese of the West Coast were derived from the earliest stocks dating back to 1–2 million years (based on several DNA studies cited). They then began spreading eastward, reaching the east coast, and spread south to north as glaciers receded. He postulates that there were reciprocal waves of movement of geese from east to west and west to east, as glaciers advanced and retreated, creating the intertwining evolutionary branches. For the situation where the nearest neighbor was not the closest relative, he “cherry picks” from several DNA studies, going back to 1977, to support his schema.
Chapter 13 discusses the taxonomy of the white-cheeked geese, comparing the American Ornithologists' Union's (1957) classification with Hanson's, although he has difficulty deciding to which AOU subspecies many of Hanson's should be assigned. Intergradation among taxa is examined from high and low tundra, Hudson Bay islands, Hudson Bay lowlands, and the Aleutian Islands. He then explores intergradations among stems of the large geese and provides common names for Hanson's taxa and the undescribed taxa within each of his stem allospecies (table 13.4 for large geese and table 13.6 for Arctic geese). It is interesting to note that B. c. parvipes is apparently included within B. c. travererni, yet Hanson and Anderson (Hanson 2006) use B. c. gavini as the “6th stem” of Arctic geese.
The last two chapters, 15 and 16, cover demographics, management, hunting, distribution, and a guide to identification. The value of these chapters depends on the interests of the readers and they will probably have little of value for most.
The final section of color plates illustrates some of the color and pattern characters used in the scoring or the cluster-analysis dendrograms in chapters 10 and 11 (plates 1 and 2). Plates 3 through 23 are dorsal and ventral photos of 96 taxa, illustrating examples of all 9 stems of large species from figure 10–1 (plus B. occidentalis occidentalis) and all six stems of Arctic geese from figure 11–1.
Anderson presents different totals for specimens examined at different places in the book (e.g., 2,090 large geese and 2,555 in chapter 10; 1,278 Arctic geese and 1,712 geese, respectively, in chapter 2; and a total of 4,500 elsewhere). Banks reported that Hanson had more than 1,800 skins and skeletons, but Anderson's totals indicate a large number (estimated at ∼2,000) that have not been reported on. Plus, he cites at least six undescribed taxa and undoubtedly will formally characterize his new name combinations in a fourth volume.
Richard C. Crossin and I visited Bert and his wife in the early 1990s. We were impressed with his collection even then, and amazed by his intricate knowledge of individual specimens and their provenance without looking at the tags. The huge collections of white-cheeked geese assembled by Hanson and Anderson pose a major problem. The holotypes for Hanson's taxa have been deposited at the Field Museum of Natural History, but the Illinois Natural History Survey apparently retains most of his specimens, although it has dispersed the bulk of its vertebrate collections. What will happen to Anderson's ∼2,000 specimens?
Finally, some judgment must be made on the contribution of this work, which represents untold years of effort by two skilled biologists. There are many flaws in this volume, both taxonomic and editorial—not surprising in the publication of a manuscript of this size, written by one author over many years and completed by another, whose views sometimes differed. There is no question that they have demonstrated that white-cheeked geese exhibit a degree of morphological variation that may be unique in the ornithological world and certainly is not elucidated by DNA studies to date. Incidentally, in seven studies of white-cheeked geese from 1957 to 2003 by other authors that involved over 1,600 samples, not a single voucher was saved, which essentially negated most of their value, and which certainly cannot be reproduced considering the amount of variation in small geographic areas proved by the studies of Hanson and Anderson. Banks (2007, 2009) concluded that these tomes negated the solid work done earlier by Hanson. Reluctantly, this author believes that the AOU Committee on Nomenclature should petition the International Commission on Zoological Nomenclature to negate all names and name combinations proposed in these works, considering the lack of competence and interest in alpha-taxonomy today.