A review by Noel Snyder
Peterson Reference Guide to Woodpeckers of North America
by Stephen Shunk
Houghton Mifflin Harcourt, 2016
298 pages, $35–hardcover
This is an attractive reference guide to the twenty-three extant woodpecker species occurring regularly north of the Mexican border since European settlement. The number of species recognized in the region has fluctuated over the years, due mainly to changes in taxonomy: The sapsuckers and the flickers in particular have undergone repeated splits and lumps, and more may follow in the future. Also included in this guide is the Ivory-billed Woodpecker, whose existence has not been confirmed for several decades but whose conservation woes continue to be a timely subject for discussion. An important compilation of diverse materials, the book is apparently intended for a readership of serious birders and scientists alike.
The guide begins with an interesting and quite detailed introduction to woodpecker anatomy, behavior, ecology, and conservation. The bulk of the book consists of species accounts that summarize much of our current knowledge about ABA Area woodpeckers. Many aspects of woodpecker behavior are illustrated with superb photographs, and the text includes discussion of various obscure ecological and behavioral idiosyncrasies that will be new to many readers.
Each account ends with a list of references, and there is an extensive bibliography at the end of the book. Nevertheless, the presentation of facts in the text is not keyed specifically to individual sources, making it difficult to track down the origin of many of the pieces of information presented. Evidently, a considerable amount of the information included comes from personal observations and conclusions drawn by the author, but in many instances that is not made clear. While the absence of comprehensive citations enhances the text’s readability, readers seeking to confirm many of the things presented here are faced with a substantial time investment to track the original sources down.
Time and space make it impossible for this review to represent such a fact-checking expedition for every species. For the present purposes, I shall focus on one species in particular, the Ivory-billed Woodpecker, for which my familiarity with the publication record is greatest. But first, I offer some remarks about the overall plan of the book.
After a brief introduction, each species account is divided into sections on distribution (breeding range, seasonal movements, winter range, map), habitat, detection (vocal sounds and behavior, non-vocal sounds), visual identification (adult, juvenile, individual variation, plumages and molts, distinctive characteristics, similar species, geographic variation, subspecies, hybridization), behavior (breeding biology, dispersal, feeding, territory defense and sociality, interactions with other species), conservation (habitat threats, population changes, conservation status and management), and references. The species accounts are followed by acknowledgments, a glossary, a bibliography, and an index; five appendices provide measurements of each species, nest site data, parenting data, a woodpecker “family tree,” and a summary of woodpecker conflicts with humans. All together these materials constitute an impressively comprehensive, convenient, and up-to-date reference to the biology and conservation of North American woodpeckers.
I turn now to a detailed analysis of Shunk’s treatment of the Ivory-billed Woodpecker, Campephilus principalis.
The value of any reference work depends on the accuracy of its facts and the defensibility of its conclusions. Having spent considerable time wrestling with the extensive literature on the Ivory-billed Woodpecker, I was especially interested to read the account for that species, in part as a preview of how analytical and how accurate the author’s treatments might be over the entire book.
I was for the most part relieved to see that Shunk’s discussion of recent Ivorybill sightings is about as noncommittal as could be, granting skeptics and advocates alike a full measure of respect, even in those cases where it might not really be deserved. Someday there may be a thorough analysis of the implications of recent and controversial claims of rediscovery, but that analysis is not presented here—and I agree that this guide is probably not the appropriate home for such an effort.
As to the earlier history of the Ivorybill, it is good to see that Shunk appears to acknowledge the consistency with which early observers asserted the commonness or even abundance of this species, historical assessments badly misrepresented or ignored in most recent writings. At the same time, however, he presents without comment James Tanner’s estimate in The Ivory-billed Woodpecker (1942) of a maximum density of just one pair per six square miles in the very best habitat, an estimate that hardly suggests abundance. Tanner’s estimate was based almost entirely on extrapolations from Arthur Wayne’s collecting data from the Wacissa River of Florida in the 1890s. Unfortunately, Tanner seems never to have seen some of Wayne’s own writings on this population—writings that strongly suggest an actual Ivorybill density an order of magnitude greater than Tanner’s estimate and comparable to the densities shown by Pileated Woodpeckers in good habitat.
Tanner clearly recognized that his estimate of maximum density was not consistent with the possibility that the species might once have been abundant. But his response to the apparent contradiction was not to question his estimate; it was instead to deny that the writings of early naturalists indicated abundance: None of the early accounts of the Ivory-billed Woodpecker contained accurate or definite statements as to the abundance of the bird. If we were to judge only from the interest that naturalists and collectors had in the Ivorybill, and the accounts they wrote, then it would be easy to believe that it was never common.
However, as David Brown, Kevin Clark, and I documented in our 2009 Travails of Two Woodpeckers, there are indeed numerous “definite” contemporary claims that this species was common or abundant in numerous locations, while essentially none of the early observers suggested that it was rare anywhere but at the very fringes of its range. It was only late in the 19th century that accounts of the species’ rarity in the central parts of its range began to appear.
The issue of early abundance is far from trivial. If the Ivory-billed Woodpecker was once common, it is difficult to justify Tanner’s characterization of the species as a diet specialist dependent on huge areas of virgin forest and threatened mainly by habitat destruction. And if it was once abundant and not a diet specialist, perhaps the Ivorybill’s decline may have been caused by something other than habitat destruction. Early writings on the species raise an alternative explanation: Its great size, noisiness, approachability, fine flavor, and high trophy value made the Ivorybill an attractive target for hunters. The hypothesis that shooting was behind the species’ decline is not undermined by the recognition of the species’ early abundance. But Tanner’s hypothesis is.
Shunk barely mentions shooting as a threat, and he leaves unquestioned Tanner’s assertions about the Ivorybill’s extreme food specialization and the stress caused by habitat loss—even though Tanner never presented any quantitative diet data demonstrating food specialization in the species, and the data from early stomach analyses and writings suggest that the woodpecker was anything but a generalist. Even Arthur A. Allen, Tanner’s major professor at Cornell, concluded in 1937 in the pages of the Auk that apparently Ivorybills were as adaptable as other woodpeckers in their food and feeding habits…so that we shall have to look in other directions for reasons for their disappearance.
Singer’s own work in the Singer Tract casts more doubt on the idea that the species was suffering mainly from food supply problems caused by timbering. That population, the only Ivorybills ever closely studied, had already declined to virtual extinction before timbering even began, and was still exhibiting reasonably good reproduction during its terminal decline.
Even more doubts arise when we consider the long survival of the last known population of Ivorybills in Cuba, which was largely limited to severely devastated forest habitat in the mid- to late twentieth century.
These are not the only problems in the Ivorybill account. In a relatively minor lapse, the fine photograph presented on p. 245 and attributed to Tanner should have been credited to Allen. More significantly, I question whether there is any good support for repeating the assertion that the species was “prone to wandering with fluctuations in food supply.” Almost all observations, including Tanner’s, are consistent with extreme sedentariness in established pairs, and virtually all accounts of wandering may refer simply to the dispersal of young birds from natal areas. Shunk’s statement that the Cuban population of Ivorybills “was last documented in mature forests” is inaccurate: Those birds endured for decades in forests largely devastated by lumbering activities.
The claim that the species “strongly favors large long-horned beetle larvae” as food goes far beyond the available quantitative data, although it surely fed on these larvae sometimes. The strong emphasis on bark scaling by feeding Ivorybills, as claimed by Tanner and repeated in this guide, may simply reflect the skewed age distribution of the dead trees available to the one pair that was closely studied. Much of the information available on this species is based on an extremely small sample size, a circumstance urging considerable caution in drawing conclusions; that issue is not discussed in this account, but an awareness of the problem could substantially help readers evaluate the significance of much of the historical material presented here.
Judging from the Ivorybill account, the materials presented in the book do require critical evaluation and routine fact-checking—something that could be said of any work of nonfiction. That said, the photographs are magnificent, and the introduction and species accounts in general present a tremendous amount of engaging natural history information that is probably mostly accurate, including many matters not covered in the Birds of North America. The writing is clear and enjoyable, while the scope is encyclopedic. I expect the book to be a source that I will frequently consult.
Moreover, I largely share the author’s concern about the threats to natural forests, even though some of the woodpecker species included in the guide may be more gravely threatened by factors other than habitat loss. I believe that it would have been valuable if in his comments on conservation Shunk had said more about such overriding concerns as human population growth and excessive carbon emissions, which could easily overwhelm all woodpecker conservation efforts if current trends continue. But it is only fair to acknowledge that it has become usual in much writing (including my own) about species conservation to omit mention of these massive ecological threats, perhaps in part because of the enormous difficulties in controlling them.
In any event, as conspicuous and charismatic forest dwellers, our woodpecker species have figured prominently in avian conservation discussions of the past, and will likely figure prominently in the conservation efforts of the future. I can only hope, along with the author of this guide, that the remarkable species that still survive may continue to do so.
– Field biologist Noel Snyder had a long career with the US Fish & Wildlife Service, leading research programs on endangered species including the Puerto Rican Parrot, Florida Everglade Kite, and California Condor. In retirement, Snyder has published books examining the causes of decline in the Carolina Parakeet and the Ivory-billed Woodpecker.