Woodpecker Fundamentals


The Red-Cockaded Woodpecker: Surviving in a Fire-Maintained Ecosystem. Conner, R. N., D. C. Rudolph, and J. R. Walters. 2001. University of Texas Press, Austin, TX. 395 pp. $60.00. ISBN 0-292-71234-0.

The Red-cockaded Woodpecker ( Picoides borealis ) is a small and rather plain-looking resident of pine forests of the southeastern United States. This species often nests in small, cooperative groups or colonies with one or more male helpers, and they make their cavities in rotted heartwood of large but living pine trees. As a result, the woodpeckers are dependent on old-growth forests for their survival. Much like the Spotted Owl ( Strix occidentalis ), this requirement has made the Red-cockaded Woodpecker a central figure in many conservation controversies, including the sometimes acrimonious debate over the relative importance of maintaining biological diversity or deriving economic benefits from public and private forest lands.

Prior to European settlement, it has been estimated that there were more than 100 million ha of pine forests in the southeastern United States. And because the Red-cockaded Woodpecker can be abundant in suitable habitats, there is little doubt that at one time it was an exceedingly common species. However, as a result of widespread clearing for agriculture, extensive timber harvests in the late nineteenth and early twentieth centuries, and, more recently, the trend to convert remaining national and state forests and private timber lands to tree farms with short harvest-rotation schedules, perhaps as much as 99% of the woodpeckers' original habitat has been altered or lost. In addition, southeastern pine forests are a disturbance-maintained ecosystem, and regular fires are necessary to prevent their conversion to hardwood forests. Fire suppression has altered the structure and species composition of much of the remaining forest, making it much less suitable for the woodpeckers. As a result, populations of the woodpecker have declined precipitously over the last century. Although it was listed as an endangered species in 1968, and protected under the Endangered Species Act of 1973, it was apparent by the mid-1980s that not only was the Red-cockaded Woodpecker in danger of imminent extinction but that existing management plans were not adequate to stem the decline, let alone bring about its recovery. To cap matters off, in 1989 Hurricane Hugo hit one of the last remaining large populations at the Francis Marion National Forest in South Carolina. This stochastic, density-independent event, of the type often discussed in classrooms but rarely actually observed in detail, was devastating: approximately 87% of the nest or cavity trees and more than 50% of the birds themselves were lost in a single day.

In response to this rapid decline, ongoing research programs on the Red-cockaded Woodpecker were expanded greatly, and many new studies were instituted. This effort produced an explosion of new information about the species and the pine ecosystem upon which it depends. This book summarizes and synthesizes that information. It is written by three of the most active and productive scientists in the field, two of whom work for the U.S. Forest Service and one who is with a university. Each author has not only conducted extensive basic research but also has been closely involved with the development of specific management plans to recover the species. As a result, the book is a detailed compendium of the ecology and behavior of the woodpeckers and a thoughtful discussion of how it would be possible—and the tradeoffs that might be required—to maintain and protect this species and all of the unique plants and animals found in southeastern pine forest ecosystems. The book is rich in detail and lessons, both positive and negative, for conservation, and I highly recommend it to those interested in the biology of the southeastern United States and anyone interested in conservation biology in general.

The first chapter is a brief introduction to the impact of humans on the Red-cockaded Woodpecker. It includes some remarkable photographs of railroad logging of longleaf pine from the early twentieth century, which show in their background an extraordinary old-growth forest. The photographs remind us how much we have changed this and most other habitats. The second chapter sets the stage for the rest of the book by discussing the southeastern pine ecosystem in detail. This pine habitat contains a number of unique species in addition to the Red-cockaded Woodpecker, many of which are now of conservation concern. As in most long-needled conifer forests, periodic but low intensity surface fires are critical here to maintaining an open tree structure and a grassy understory. However, unlike the western Ponderosa pine ( P. ponderosa ) forests that have been the subject of much attention lately, where fire is critical for killing pine seedlings and preventing the development of dense thickets that can lead to catastrophic crown fires, surface burns in the Southeast function to prevent the recruitment of other non-pine species. When fires are suppressed in these ecosystems of the Southeast, the ultimate result is habitat loss through a conversion of the pine forest to those dominated by oaks, hickories, and other hardwoods. Even before this conversion is complete, however, research has shown that fire suppression will affect Red-cockaded Woodpeckers in many ways—ranging from an increase in pine mortality due to beetle outbreaks to a reduction in available foraging habitat—because the birds tend to avoid searching for food in areas that are near dense understories of deciduous trees. Thus, one key element of any conservation strategy for the Red-cockaded Woodpecker is to return fire to its natural role in the pine forest ecosystem.

Chapter 3 is a brief introduction to the Red-cockaded Woodpecker's taxonomy and morphology, including a possible explanation for its common name. The males have a small patch of red feathers on their heads, which apparently looked to Alexander Wilson, an early American ornithologist, like the cockades or badges on the hats of soldiers in the colonial army. Because these feathers are rarely visible except when the birds are held in hand, the name is not particularly appropriate ( but also inappropriate is the bird's scientific epithet, “borealis,” because the species has an entirely southern distribution in the United States ). With respect to its conservation, what is important is that there is nothing particularly exceptional about the Red-cockaded Woodpecker: it is not highly specialized and does not have any unique ecological requirements that would make it an evolutionary dead end, as is sometimes claimed for many other species that are now in danger of extinction. Rather, it is a typical woodpecker in both morphology and behavior, which had the misfortune of adapting to a habitat that was once extremely widespread but that is now also highly coveted by human beings for their own uses.

Information about changes in the distribution of the woodpeckers is summarized in the following chapter and includes the familiar pattern of both declining abundance and increasing fragmentation of existing populations. What is exceptional here is the amount and quality of range-wide data for the species. Obtaining even order-of-magnitude estimates of the total number of individuals of a widely distributed species is almost impossible in most cases, but the cavities made by the woodpeckers are easily recognized. Also, whether or not the cavities are currently being used can usually be determined by whether or not sap is flowing around the cavities edges ( the birds make sap wells and keep them open to deter snakes and possibly other predators from entering the nest ). Using past summaries by Jerry Jackson, Fran James, and others, and their own work, the chapter authors estimate that populations have declined from what may have been upwards of 1.6 million groups or colonies in presettlement times to 6000–7000 groups in the early 1970s to <5000 in the early 1980s and <4000 by the early 1990s—a loss of more than 99.7%. Cavity surveys are still underway, and, in a very positive note, the authors indicate that this trend may now have begun to change. As a result of new conservation efforts, population numbers appear to be stable or increasing in areas where there is intensive management, although the woodpeckers are still declining where there is not.

The remainder of the book is a masterful summary and textbook example of how a basic understanding of its biology can be used for ( and is critical to) promoting the recovery of an endangered species. Two factors appear to be most important for the Red-cockaded Woodpecker. The first concerns the fact that the birds make their nest and roosting cavities in live trees. Most woodpeckers excavate holes in either dead trees or in live hardwoods. Live conifers are almost never used because the sap produced by the trees in response to the injury will flood the hole and eventually kill the eggs or any hatched young. However, dead trees often are burned in fires. Therefore, in the original, frequently burned pine ecosystems in the southeast, such trees likely were not usually available. The Red-cockaded Woodpecker solved this problem by using living pine trees, but only ones where the heart wood was dead and sap was not flowing. This is most likely to occur in the older and larger trees. In addition, heartwood decay can be promoted by fungi, often Phellinus pini, which is more common in older pines and which makes a cavity easier to excavate. As a result, the birds require trees that are relatively old: estimates of the average age of cavity trees are often between 100 and 130 years and may range between 49 and 332 years.

This need to nest and roost in old trees where there is no sap flow in the heartwood means that silvicultural practices that remove the older trees and shorten rotation times between harvests will lead necessarily to the loss of the woodpeckers in that area. The situation is complicated by the fact that the birds can require many months or years to excavate a new cavity, and they are highly vulnerable to predation without cavities in which to roost at night. Thus, it is almost impossible for the birds to naturally recolonize an area once the original cavity trees have been lost, even if there are trees that are large or old enough in the area. This means that a conservation strategy that relies on the gradual maturation of the forest to provide old-growth trees sometime in the future would necessarily fail. Indeed, many of us who became acquainted with the woodpeckers during the 1980s, when populations were rapidly declining, were convinced ( albeit usually secretly ) that the woodpeckers were probably doomed to extinction.

Fortunately, an understanding of the central importance of nest cavities to the woodpeckers, and the special conditions under which they had to be constructed, led to a solution. If the birds could not make their own cavities, then why not make new cavities for them? This was first tried as part of an experiment in 1989 by Carole Copeyon, a student of Walters, and was subsequently developed by various other groups. The idea is simple: either drill a new hole into the heartwood or construct an entire artificial cavity that is then inserted into a sawed-out section of the tree. Remarkably, the birds readily adopt these new holes. This conservation innovation has given managers a power tool because it allows them immediately to replace cavities that have been lost through natural or unnatural events and thereby maintain existing groups until there are trees old enough for the birds to excavate their own replacement cavities.

The second major advance was the development of effective translocation methods, which in turn was dependent upon a detailed understanding of the birds' social behavior and dispersal patterns ( chapter 6 ). In part because cavities are so important but very limited in number, many young males stay at home and become helpers at the nest rather than dispersing to breed in new territories ( most females leave their natal groups and attempt to pair with a nearby unmated male ). Although there are many interesting theoretical questions about this type of breeding system, it has profound consequences for the conservation of the woodpeckers. In particular, as habitat quality declines through loss of old trees and invasion of hardwoods as a result of fire suppression, young males do not disperse in search of better areas but rather often stay at home. Eventually, as the older birds die off, many territories become occupied by single males. This limited dispersal, which is typical of most cooperative breeders, prevents the colonization of new areas and leads to naturally fragmented populations. In addition, females appear to have difficulty finding males when they are widely dispersed, accelerating the population decline. Once this problem became understood, the solution was again apparent. Effective techniques have been developed to move young females into territories of unpaired males territories and place them into an unoccupied cavity at night. The next morning, the female is allowed to leave the cavity with the hope that it will then pair with the male. In addition, pairs have been translocated successfully into previously unoccupied habitats by placing them in artificial cavities. Because the birds do not require extensive stands of old-growth forest for foraging, this technique allows managers to return birds to areas they once occupied but left in a “dispersal event,” something the birds never could or would do on their own.

The final chapters address other factors that affect the woodpeckers, as well as past, current, and possible future management practices. Ultimately, of course, the goal is to restore a functional pine forest ecosystem with sufficient old-growth trees to allow for the construction of new cavities by the woodpeckers. But many intermediate steps can be taken along the way to help the birds and the other species that depend on this ecosystem. Many of these steps are described in the new draft recovery plan for the species that the authors helped write. Whether or not the plan will be adopted in the current political climate remains unclear. The authors have been in the trenches with these issues and have at least occasionally experienced the personal consequences of being the bearer of bad tidings. In spite of this, there is no anger in their discussions or blaming of others for past failures. What I sense is a cautious optimism for the future of the Red-cockaded Woodpecker, along with perhaps a sadness that management practices that have proven effective may not be adopted.

As this book clearly demonstrates, we now know enough about the Red-cockaded Woodpecker to ensure its survival. To me, the very wealth of detail on the woodpeckers contained in this book raises troubling questions about the state of conservation biology and resource management in the United States. For many of the species that have declined precipitously in the last 50 years and that are now listed or are candidate species under the U.S. Endangered Species Act, we know little about the specific factors or management practices that have led to their declines. This lack of information is often used to justify conservative or minimal management action to promote the recovery of a species. As a result of the dedicated work of the authors of this book and many other scientists inside and outside of government, there is little doubt that we can insure that the Red-cockaded Woodpecker will not go extinct while at the same time continuing to obtain economic benefit from southeastern pine forest ecosystems. It is no longer an issue of one or the other as far as this species is concerned; we can have both if we accept some limitation on single-minded resource extraction for short-term economic gain. Whether we have the political will to do so is the primary remaining question. I hope that 10 or 15 years from now the authors will produce a second edition of this volume that will include not only the results of new research but also a final chapter chronicling the initial decline and subsequent recovery of the Red-cockaded Woodpecker and the extraordinary ecosystem upon which it depends.