Loon Lessons: Uncommon Encounters with the Great Northern Diver

Loon Lessons is an easy book to review because it is so good. Filling a huge gap in synthesized knowledge about this species since Judith McIntyre’s The Common Loon: Spirit of Northern Lakes (1988), it contains everything that is currently known about the Common Loon (Gavia immer), a species for which the southern portion of its breeding range has moved northward over the past 100 years. Through a fascinating combination of scientific research and anecdotes of the life experiences of the author, Dr. James Paruk, this book reviews some of the more significant knowledge that has been gained both from past and current research, and considers some of the more important questions faced by this species that should be addressed with future study. The book begins with three chapters that review what is currently known about the evolutionary history of the entire family of loons (Gaviidae) as well as the anatomical and physiological adaptations that distinguish loons from other species and have made them so successful as foot-propelled diving birds. Paruk divides each chapter into very accessible subsections (e.g., loon diversity, functional explanations of a breeding Common Loon’s “necklace” and “checkerboard” back, anatomical and physiological adaptations in specific muscles and tendons) that allow the reader quick access to select certain topics that are of greater interest. As a seasoned loonist, while I was not so much interested in learning about the physics of bird vocalizations, I was particularly fascinated by Paruk’s discussion of the physiological challenges loons face in staying warm. Following these, Paruk delves into a series of chapters that review some of the more fascinating aspects of the behavioral ecology of the Common Loon, often approaching these as an economist by describing certain behavioral characteristics, such as prey selection, as functional trade-offs between individual benefits and costs. For example, Paruk states “Cost-benefit analysis predicts a point of diminishing returns for a loon trying to fill its belly on small prey, unless they are superabundant and relatively easy to catch. Therefore schooling fish… are main components of a wintering loon’s diet.” We are able to consider these behavioral trade-offs because of the development of effective techniques to capture and mark individual loons with colored leg bands in the early 1990s. As Paruk aptly notes, by watching individuals that can be confidently identified from these leg bands, we have learned so much. We have learned that loons are prolific diving birds, as they can dive and remain underwater for up to four minutes. We have learned that loons return to both the same breeding lakes and wintering areas year after year, and, though the public may still not believe it, loons don’t always mate for life. We have learned that loons, like many species, can change from being highly territorial (they kill each other and their chicks) to being highly social during the course of the breeding season, and loon behavior may vary depending on the type of breeding territory they possess. Paruk’s discussion of loons breeding on a lake that supports only one single pair (single-pair lakes) in comparison to loons that defend a part of a lake that supports multiple pairs (multi-pair lakes) was particularly close to my heart because of the limitations of my work considering the impacts of lake acidification on loons to the former, as I never had to consider the fact that loon pairs on multi-pair lakes have to fend off neighboring pairs in addition to unpaired individuals that want to usurp their territories. Throughout these informative chapters, Paruk presents these findings through not only presenting the theoretical underpinnings of the subject, but also through the data that have been gathered by so many scientists. These are made more poignant because of Paruk’s personal relationships with those who are doing this work in the field today. At the end of each chapter, Paruk provides a Further Reading section that provides the reader with an excellent series of references to primary literature (though somewhat lacking in Canadian contributions) that the reader will likely find quite useful. The author surmises the northerly regression of the breeding range of the species has resulted from the loss of shoreline nest habitat and high rates of nest predation, both resulting from increased anthropogenic activities. In response, managers and citizen scientists have constructed and deployed floating nest platforms that have greatly enhanced loon productivity on highly-developed lakes. However, Paruk also aptly notes some of the other threats loons currently face, including toxicosis from the ingestion of lead shot and fishing tackle, the loss of prey and enhanced rates of methylmercury poisoning that have been exacerbated in certain areas because of high lake acidity, direct and indirect poisoning from oil spills, and pathogens that transmit diseases such as avian malaria, West Nile Virus, and avian influenza. Black flies have been recently noted to harass loons, especially during incubation, and can be a serious problem. Paruk considers how such threats currently impact loon populations, but not how they will likely change in the advent of a changing climate. While reinforcing what has been learned, the book also points out gaps in knowledge, such as the explanations of the loon’s red eye during the breeding season, the great variability in migration routes among individuals (some loons that breed in Saskatchewan winter off of the Pacific coast, and others that breed in the same area winter in the Gulf of Mexico) for a species that experiences such high wing loading, and the lack of understanding of why some loons choose to overwinter on freshwater reservoirs and lakes. Loon Lessons is not one of the many coffee table books on loons. It is an extremely readable synopsis of current research and collection of life stories that is of great interest to biologists, field workers, citizen scientists, cottagers, canoeists, and anyone remotely or greatly interested in loons. The illustrations, maps, and photographs are excellent (though the maps could have used a bit more contrast), and greatly complement Paruk’s wonderful narrative. The only thing I thought a bit odd as I read this book was the choice of the subtitle. What precisely was uncommon about the encounters, and why did Paruk choose the name Great Northern Diver, as it is used only in the Old World, where the species barely occurs? Regardless, I found the book to be a great synthesis of the life history, status, and conservation needs of such an iconic species of freshwater lakes. Book Review Editor: Jay Mager, jmager@americanornithology.org

Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.