Ecological and Environmental Physiology of Birds is an eclectic summary of current thought in the field of avian ecological physiology. The book is designed to provide a concise and current overview of physiological ecology in birds for graduate students, beginning researchers in comparative physiology, and ornithologists. The contributors to this book are a diverse group of ecological physiologists from around the globe, most with an academic pedigree linking them to early pioneers of the field. Eduardo Bicudo studied with Knut Schmidt-Nielsen, Mark Chappell with George Bartholomew. William Buttemer and James Pearson studied with mentors who were students of Bartholemew. Claus Bech was supervised by Kjell Johansen, who did his PhD work at the University of Oslo, where Per Scholander was a professor of zoophysiology. Each contributor brings his extensive research background to the text, adding to our knowledge of how avian biology functions at a mechanistic level.
Born of a marriage between comparative physiology and natural history, the discipline of ecological physiology is intended to explain how the physiological machinery of organisms enables them to cope with their changing natural environment and how natural selection has modified, and continues to modify, physiological phenotypes to solve difficult environmental problems. The field emerged during the late 1940s and early 1950s with Schmidt-Nielsen's exploration of how kangaroo rats could survive their desert environment without drinking water, Bartholomew's work on the electrolyte balance of birds in deserts and in salt marshes, and Scholander's research on the respiratory physiology of diving marine animals. A common theme in their research was a fascination with the myriad ways in which free-living animals functioned in their natural environments (Schmidt-Nielsen 1987, Dawson 2005, Weibel 2007).
Studies of birds by these scientists played a prominent role in the development of ecological physiology. Interested in how marine birds could survive without drinking freshwater, Schmidt-Nielsen discovered avian nasal salt glands, which are extrarenal structures that allow marine birds to drink seawater. Later, he discovered that airflow in the bird lung is unidirectional (unlike that of mammals), an adaptation that allows birds to fly at high altitudes. Bartholomew modeled how seed-eating birds could survive without drinking and elucidated the circumstances under which metabolic water could supply all of a bird's water requirements. Scholander measured the heat loss of small Arctic birds, which resulted in the Scholander model of heat transfer for endotherms, which is taught in animal physiology classes today.
As a result of this research into avian physiological adaptation, a fascination has developed about birds' ability to occupy nearly every habitat on Earth, including the cold Arctic and the hot deserts of the world. A better understanding of how birds live where they do is necessary as our global climate patterns change. Birds have unusual physiological attributes—higher rates of metabolism, higher body temperatures, and higher plasma glucose levels than mammals of similar size—yet they have a longer life span. Examining the physiological machinery in birds may explain the differences in life histories and could be important in our quest to understand human aging.
Ecological and Environmental Physiology of Birds begins with a discussion of the evolution of birds' body plan, with an emphasis on feathers and flight. This first chapter also includes sections on molt, nocturnal migration, and the energy cost of flight in flocks. The second chapter is devoted to basic physiological principles, such as gas exchange, heat exchange, and osmosis. The remaining chapters cover a variety of topics, including associations between avian physiology and life history, how birds obtain and process food, neural and sensory physiology, the developmental physiology of nestlings, and a discussion of special adaptations that birds exhibit in specific environments. The authors conclude with an overview of current techniques used by investigators to assess physiology in birds, especially energy expenditure, and remark on future directions in the field. The book is thought provoking, covers a broad range of topics, and includes research from over 1100 publications. The chapter on avian fecundity and life-history trade-offs is especially well written and provides insights into the complex connectivity among the endrocrine system, the immune system, metabolic rate, and the rich variation in avian life history. As a graduate student text or as a research reference, the book fills an important niche in ornithological literature and will stimulate future research in avian ecological and environmental physiology.
Despite my enthusiasm, however, I note a few limitations in the book that, to me, detract from its impact. Organizational problems, for one, led to some repetition within and among chapters. For example, chapter 2 describes water loss in bird eggs (pp. 32–34)—information that is reiterated in chapter 7 (p. 211). Chapter 5 discusses the thermal consequences of a marine lifestyle (p. 169), citing the unique plumage of cormorants (Rijke 1968). After a section on locomotion, the authors revert to another discussion of thermal exchanges, again citing the unique plumage of cormorants (pp. 179–180). The rate of heat loss in water is discussed repeatedly in these sections. In addition, some undefined words in the text may be confusing to beginning students—pallium, neritic water, arcopallium, hyperstriatum, parasagittal, to name a few.
Minor conceptual errors or assertions having alternative explanations are also present. An example of this is that the authors claim on page 1 that birds are viviparous (live bearing) instead of oviparous (egg laying), and on page 3 the authors suggest that flight in birds evolved during the late Jurassic period when the atmosphere was hyperoxic and hyperdense, with about 31 percent oxygen (10 percent higher than present-day oxygen levels). An analysis based on carbon isotopes of organic matter and carbonate samples collected from the Atlantic basin show, however, that during the late Jurassic, oxygen concentrations rose to current levels—21 percent, not 31 percent (Falkowski et al. 2005). On page 39, the book claims that the skin of birds is impermeable to water-vapor diffusion, but later, in chapter 5, the text describes water-vapor diffusion through skin as an important component of total evaporative water loss.
A lack of acknowledgment of certain authors who performed seminal work in the field is apparent. For example, on page 128, the book states that egg laying appears to increase daily energy expenditure by about 35 percent, with attribution given to Charles T. Robbins's book on wildlife ecology (1993), yet the major contribution of Jim King (1973, 1974) on the cost of egg laying, that of Bob Ricklefs (1974), and the more recent work of Tony Williams (2005) are all overlooked. On page 149, the book addresses seasonal and latitudinal adjustments of metabolic rate: The basal metabolic rate tends to be higher for birds in cold climates or higher in winter than in summer. It might have been appropriate here to include the work of Dave Swanson, who for the last decade has examined variation in rates of metabolism relative to the environment (Swanson 2010). Finally, on page 189, the book describes how African gray parrots use words in numerical and relational concepts—abilities once thought unique to humans. This would have been an appropriate place to cite Irene Pepperberg's (2000) work on African grays. Pepperberg demonstrated that a parrot named Alex could differentiate meaning and syntax in his language skills; his communication was not instinctive but, rather, learned.
Despite its shortcomings, Ecological and Environmental Physiology of Birds provides a concise overview of the current literature in avian physiology for beginning researchers, and it should stimulate discussion in lab groups and with graduate students. The book illustrates how far research in the field has come and how many topics are yet to be explored.
