Invasion biology has often been criticized for its dissociation from the rest of ecology and its lack of rigor in adopting and rejecting new hypotheses and theories [1xInvasion Biology. Davis, M.A. See all References][1]. A new book by Blackburn, Lockwood and Cassey proves that this is no longer true. In this book, three leading experts combine theory with a rigorous analysis of the evidence to ask what are the causes and consequences of avian invasions. And they succeed formidably.What sets this book apart from others is its focus on a single group of organisms: birds. Whereas this reduces generality, a detailed knowledge of the studied system is essential to interpret and integrate findings into a coherent framework.Why should birds be a good model system in invasion biology if their economic and ecological harm is less than that of other organisms? The reason primarily lies in the high quality record of past avian introductions, which provides unique opportunities for research. The book is largely built on the enormous body of evidence drawn from the analysis of these historical introductions, which for some will be the strength and for others the weakness of the work. A comparative approach provides general results that apply across taxa and over broad regions, and allows for questions to be addressed that would be difficult to answer with experimental approaches. Nevertheless, past introductions were not well-designed experiments and have their own shortcomings. The authors discuss these shortcomings and convincingly argue that the comparative analysis of past introductions is still a powerful tool provided that its limitations are acknowledged and appropriate statistics are used.Avian invasions is set out in two sections that respectively cover the causes and consequences of invasions. The chapters on the causes decomposes invasion into four stages: transport, release, establishment and spread. These stages are not only governed by different processes, but each stage shapes the subsequent stages both for ecological and non-ecological reasons. For example, evidence is provided in Chapter 2 for a non-random pattern in the species that are transported and introduced, and the regions where they are released. Because this non-randomness could confound efforts to identify factors that influence subsequent stages, the authors advocate use of transport and introduction patterns as a ‘null model’ in invasion biology. The authors adopt this null model when asking why alien species can succeed in establishing and spreading in environments to which they have not had the opportunity to adapt. The paradox is classically resolved by invoking pre-adaptations to the new environment and environmental conditions that increase region invasibility. However, in Chapter 3 the authors propose a simpler explanation: luck. Most avian introductions involve a few individuals and consequently many populations die out as a result of stochasticity and Allee effects. Beyond a certain number of individuals released, however, success is no longer determined by propagule size. The properties of the species and locality gain then greater importance. Chapter 4 proposes that key adaptations during establishment reduce Allee effects and assist individuals in finding appropriate niches in the novel environment, notably ecological generalism and behavioural flexibility. Whereas these latter traits could aid establishment in regions where invasive species have had no opportunity to adapt, in Chapter 5 the authors show that establishment is also facilitated if the environment is climatically similar to that found in the native region of the invader and has been altered by human actions. This highlights the importance of species-by-habitat interaction during invasions.The second section, as fascinating as the first, focuses on the consequences of invasions. Biological invasions enable researchers to study ecological processes in real time, rather than inferring them, and this provides unique opportunities to address important issues in ecology and evolution. For example, we read that exotic birds influence biodiversity patterns primarily through changes in entry rules, and that the common view that invaders pass through a genetic bottleneck during the first stages of the invasion process does not hold for birds. The authors also propose that avian exotics provide some of the best evidence of contemporary evolution by natural selection.Overall, I very much enjoyed reading Avian invasions. It is informative, comprehensive, rigorous, stimulating and highly readable. The book is a must read for anyone interested in biological invasions, and will inspire students and academic researchers alike.