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1 October 2012 Interspecific Competition in Birds
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This book is a rich source of inspiration for anyone interested in competition and how the presence of competitors is manifested in the daily life of birds. It is a timely and welcome integration of knowledge on several levels of organization— community, population, and individual. For ecologists, competition has become something of a Holy Grail, eagerly sought but evasive. It is attributed a key role in both evolutionary theory and population dynamics. Yet the role of competition remains controversial, and its mode of operation is rather abstract when deduced from limiting similarity or niche separation. As manifestations of competition, such patterns reflect the “ghost of selection past” rather than illustrating its mechanisms in operation. Here this new book by André Dhondt comes to our aid, giving competition a more concrete form in showing how individuals monitor daily threats to survival and their prospects of reproduction. The book pulls together a wealth of field data demonstrating how the presence of competitors affects the individual's behavior. The data span several levels of organization, ranging from density-dependent responses on a population level, to between-individual behavioral interactions, and, in particular, to individual strategies of efficient resource use in a competitive environment.

The book reflects how rich the study of competition of birds in the wild can be—it can include more than linking numbers to population growth. Dhondt lays bare a wealth of between-individual behaviors and individual—resource relations demonstrating responses to resource depletion and how individuals handle their social environment. The reality of competition can, for instance, be read from individual differences in their strategic responses to a dominance-structured society. Individual differences in behavior reflect adaptive responses in habit use, time allocation, and energy storage. Eventual evolutionary consequences of such individual differences are manifested in survival and reproductive success. Population dynamics and adaptive strategies here go hand-in-hand. This book amply demonstrates how competition is more than a mere abstraction with such a multilevel approach, but it also shows how painstaking the quest to unveil the operation of competition in the field can be. The main value of this book lies in the impact of the combined detail of data from an array of meticulous field studies on different organization levels—population, between-individual, and individual—and how their conclusions converge. It is hard to put this book aside without being convinced you have seen competition in the wild as a reality.

The book addresses data from bird studies in particular. The reader must, however, be aware that “birds” in this context is largely equivalent to tit and titmice species (genus Parus before it was recently split into several genera). As early as page 4, the author exclaims “Tits come to rescue.” Other species do come in, but it is abundantly evident that André Dhondt primarily thinks in terms of tits and titmice. The selection of material may seem narrow given the title, but this is no coincidence. In fact, the concentration on this genus is due to the fact that no other bird genus is likely to have been studied more intensively on different levels of organization in the field. Several Parus species that differ in many aspects of their ecology have a long history of study. To a large extent, this book is an excursion in behavioral ecology from a tit's perspective. Overall, a focus on the tits—and, in particular, the quality and diversity of data from these studies—allows a coherent approach to the role of competition, and it comes out more as a strength than a limitation of the book. The combined weight of these data makes it possible to link processes governing inter-individual relations on different organizational levels.

The book's title promises to address interspecific competition, but this is treated with great latitude. Interspecific effects do get their share. We are, for instance, presented with the unique long-term data on how the Great Tit and the Blue Tit mutually affect each other's numbers. Yet considerable attention is equally given to within-species competition and individual behavior, and this allows the treatment of competition to be more than an excursion in the theory of mutual influence on numbers. Dhondt can dissect in incisive detail how the presence of competitors profoundly governs how individuals go about securing their survival and how they invest in reproduction. In this he can draw heavily on the emergence of behavioral ecology as a separate field of study. Dhondt is exceptionally well placed to draw together this information with his own Parus studies, which straddle population biology and behavioral ecology. The book relies on the progression of approaches to competition in studies of bird populations in the wild. Competition studies were initially based on population census data aimed at detecting density dependence, reflecting the influence of David Lack. With the emergence of behavioral ecology, the census data were complemented with studies of social organization and strategies on an individual level. Here, Dhondt goes beyond the idiosyncrasies of the single studies to show their relevance for population dynamics and community structures.

André Dhondt has done us a great service in bringing all this information between two covers. If there is any weakness of the book, it is a Northern Hemisphere bias. Extrapolating conditions from the largely temperate and boreal environments of the Northern Hemisphere to the largely tropical and subtropical environments of the Southern Hemisphere requires a leap of faith. The author cannot be blamed for this, for it reflects the state of the art. The limited geographic distribution of population studies of birds in general, and of Parus species in particular, should serve as an incentive for future studies. This book provides a rich source of ideas and should serve as inspiration for any young biologist who aspires to study population biology in the wild. In particular, it is successful in managing to express in plain terms how the presence of competitors is manifested in the everyday life of an individual. It has a natural place on the desk of any biologist interested in the role of competition as a structuring force in nature.

© The American Ornithologists' Union, 2012.
Jan Ekman "Interspecific Competition in Birds," The Auk 129(4), 793-794, (1 October 2012).
Published: 1 October 2012

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