Animal Communication Networks—Peter McGregor [editor]. 2005 Cambridge University Press, New York. 672 pp. ISBN 0-52-182361-7. $130.00 (cloth).

In compiling recent research advancements and prospects in the expanding area of animal behavior, this volume presents a perspective that can increase our understanding of animal communication: communication networks. Animal Communication Networks is based on the fact that communication is an inherently social behavior, and that many signals used in communication travel farther than the average distance between animals. However, the wider social context is often ignored in studies of animal communication and has rarely been considered explicitly. In adopting a network perspective, we are able to identify and explain communication behaviors that cannot occur in a dyad, such as the eavesdropping behavior of birds. The book covers several taxonomic groups (from insects to humans), and several types of signals (including visual, acoustic, and chemical). It also highlights disciplines that interact with the study of communication, such as psychology and physiology. Animal Communication Networks offers convincing evidence for the existence of communication networks presented by a diverse group of authors, including many prominent ornithologists.

The book is divided into four parts. Part 1 deals with communication behaviors, such as audience effects and eavesdropping, that involve three or more individuals and therefore fall outside of the traditional dyadic approach to communication. Part 2 explores concepts that are valuable to consider from a network perspective, such as predation and mate choice. Part 3 is grouped taxonomically, from crabs to humans, because characteristics specific to different taxa influence the properties of communication networks. Part 4 contains chapters that link communication networks to other disciplines in biology. Of the 26 chapters, each written by a different group of authors, 10 are specifically about communication in birds, including such topics as mate choice, male–male song contests, and nestling begging. In this review I will focus on these chapters and evaluate how this book may be useful to ornithologists.

In Chapter 2, Tom Peake discusses eavesdropping, focusing on the costs, benefits, and implications of eavesdropping behavior on signaling interactions. Because eavesdropping is a receiver behavior that is only possible in a communication network, I think this is an excellent way to begin the book. Peake makes convincing arguments about the occurrence and significance of eavesdropping with many examples drawn from the ornithological literature, and prompts researchers to take this behavior into account when studying animal communication. Chapter 3 deals with social eavesdropping and the acoustic signals of birds. It identifies potential costs and benefits of eavesdropping and uses information about how bird song transmits to explore how eavesdropping is best achieved. In this chapter, Torben Dabelsteen discusses how communication behavior can be made public, private, or anonymous, and how eavesdroppers should behave. Chapter 3 is short on data, but contains several suggestions for avenues of future research. Figure 3.3 highlights the results of an interesting study on the movement patterns of female Great Reed-Warblers (Acrocephalus arundinaceus), in which researchers found that females positioned themselves at equal distances from neighbouring males to listen in on vocal interactions. Apart from this example, much of the evidence used to support these ideas is experimentally based but not tested in a natural setting. This is a common thread in the book; most authors conclude their chapters with a statement of how natural, field-based research is needed to confirm experimental results derived from the laboratory or other artificial situations.

Ricardo Matos and Ingo Schlupp introduce the idea of audience effects in Chapter 4. They highlight that audience effects and eavesdropping are essentially opposite sides of the same coin, depending on the individual of interest. The authors begin by presenting useful, clear, workable definitions to introduce the topic. They include a section on human behavior that seems misplaced in light of the rest of the chapter, and was too short and superficial to be very informative here. Victory displays are the topic of John Bower's Chapter 6. He pools the available information on victory displays and interprets their functional significance from a network perspective. The main evidence he uses to illustrate victory displays is an observed increase in the winner's song rate after a contest in Song Sparrows (Melospiza melodia). However, in this case it is difficult to unambiguously distinguish a victory display from the interaction itself, especially when the signal used in the victory display was also used in the interaction (i.e., song), and it is not a display unique to winners of contests. Victory displays are virtually unexamined in birds, but Bower provides some insightful discussion to stimulate research on this topic. Part 1 ends by prompting researchers to incorporate eavesdropping into theoretical models and to look for evidence of eavesdropping in natural contexts.

In Chapter 7, Ken Otter and Laurene Ratcliffe present evidence to suggest that a communication network is a likely context for mate choice, because females are able to assess the widely broadcast mate attraction signals of multiple males. They focus on primary and secondary mate choice based on acoustic signals in territorial songbirds. They discuss how mate choice is achieved, comparing simultaneous and sequential assessment tactics, and how female movement can be used to infer sampling within a network of males. I think this chapter was one of the strongest in the book; it provided compelling evidence for female assessment using a communication network perspective. They included a section on habitat alteration that seemed out of place, but this did not detract from the overall strength of the chapter.

Nestling begging has traditionally been considered in a dyadic context, between the brood as a whole and the parent. In Chapter 9, Andrew Horn and Marty Leonard reveal how considering begging as a network can yield new insights into begging behavior and provide a model system to study the evolution of signaling. Data in the form of tables and figures were absent from this chapter, but overall the authors made a convincing argument for how concepts from communication networks can be applied to a variety of model systems previously considered dyadic systems. Section 2 concludes with a discussion of future challenges in studying a broader view of communication in model systems.

In Chapter 14, Marc Naguib combines current knowledge on strategies of vocal interactions in songbirds with concepts of territorial behavior and territorial settlement. Naguib emphasizes that singing strategies have evolved in a network environment, and thus should be studied from a network perspective. This chapter would be of interest to anyone studying territorial songbirds, and outlines ideas to consider when conducting field studies. In Chapter 15, John Burt and Sandra Vehrencamp consider the dawn chorus of songbirds from a network perspective, which seems an approach likely to reveal the function of this behavior. They begin the chapter with an excellent figure outlining three basic network structures, which is a useful starting point for a reader unfamiliar with communication networks. In particular, they outline the results of their research on interactions between neighboring tropical wrens. They used a microphone array, a new tool for investigating networks, to examine the properties of interactions among four focal males. This chapter provides compelling preliminary data, uses informative graphs to illustrate key points, and provides a good amount of background information without being overwhelming. Section 3 concludes by posing important questions for future research: how many individuals are encompassed by a signal, and what is the extent of a network?

In Chapter 20, Ulrike Langemann and Georg Klump discuss perception and acoustic communication, arguing that the sensory abilities of the receiver are often overlooked. This chapter unites communication networks, psychophysics, and physics, but is not a stand-alone chapter. For a reader new to the communication network idea, this is not the place to start. The chapter is full of physics, equations, and detailed methodology. Using this approach, the authors provides new tools to study communication and perception, but these tools are not necessarily applicable to communication networks. Irene Pepperberg highlights the need to consider nontraditional forms of experimentation on cognitive aspects of networks and avian capacities in Chapter 24. She focuses her discussion on transitive inference, and offers insight as to how to test this idea in future studies. She cites specific examples from the literature that support, or at least prompt further investigation of, transitive inference, and concludes that birds demonstrate complex cognitive processing skills. This chapter has several ideas that parallel earlier chapters on eavesdropping with an emphasis on territorial songbirds. Although Pepperberg's chapter is compelling, I think Section 4 is the weakest part of the book. While the connections to other fields of study are potentially fruitful avenues for future research, these connections are at present only minimally developed. Thus, it seems premature to include these superficial discussions in the first edition of this text, and after three strong sections based on empirical evidence from the laboratory and the field, Section 4 was a rather disappointing way to end the book.

In sum, I would recommend Animal Communication Networks to anyone interested in discovering a new approach to the study of animal communication, and I think that it will be especially appealing to those involved in research on acoustic communication in songbirds. Although a few chapters seem inappropriate for the book, overall it is a well-written compilation of a new and exciting avenue of research in animal communication.