Common loons are the subject of James D. Paruk’s book, “Loon Lessons: Uncommon Encounters with the Great Northern Diver.” Paruk, a professor of biology at St. Joseph’s College in Standish, is one of the leading experts on common loons. Robert F. Bukaty/Associated Press

Birding is an activity that brings joy to many Americans. A survey by the U.S. Fish and Wildlife Service found that over 15 million U.S. citizens are birders. Their definition is a rather lax one, requiring that a person taking just a single trip away from home qualifies as a birder. The number of hardcore birders – members of bird clubs or ornithological societies, users of eBird, enthusiastic bird listers, regular travelers to birding destinations – contains only a fraction of those 15 million people.

Nonetheless, interest in birds is high. That interest means there is a vibrant market for books on birds and birding. The number of new titles can seem overwhelming. Today, I want to provide a brief review of two recent bird books by Maine authors.

The first is “Loon Lessons: Uncommon Encounters with the Great Northern Diver” by James D. Paruk. Paruk is one of the leading experts on common loons, having studied them from Washington and Saskatchewan to the coasts of California, Louisiana and Maine. He is a professor of biology at St. Joseph’s College in Standish, an adjunct professor of biology at the University of Southern Maine and a research scientist at the Biodiversity Research Institute.

The first chapter describes the various skeletal, muscular and physiological features that make a common loon such a great diver. The next four chapters cover reproduction (courtship, nesting behavior, calls, and vigilant defense of eggs and chicks).

A chapter on loon behavior includes a detailed discussion of the foot waggle and its probable function. This behavior is also seen in diving ducks, grebes and mergansers. Interesting stuff!

Two chapters cover loon migrations and winter ecology. We learn about habitat selection, fidelity to wintering sites and diet during migration and during the winter.

Three major threats to loons are exposure to mercury, lead and oil spills. Paruk covers these threats thoroughly in a chapter that is alarming but hopeful. The final chapter is a look forward for how our changing planet will affect common loons.

His writing is crisp and clear. Twenty color photos and some black-and-white figures augment the text. I appreciate the references at the end of each chapter, allowing the reader to find original sources to explore a topic more fully.

The second book is “Duet: Our Journey in Song with the Northern Mockingbird” by Phillip Hoose. Hoose is an award-winning writer who lives in Portland. His earlier books include two birds books, one on red knots and one on the ivory-billed woodpecker.

“Duet” explores the poorly known but significant relationship between humans and the northern mockingbird. The mockingbird is renowned for imitating convincingly the sounds of many species of birds and other natural sounds.

The book is arranged in chronological order. Phil begins with a chapter on mockingbirds and native Americans. The mockingbird appears in many myths and legends, particularly with respect to the development of languages.

We learn about Christopher Columbus marveling at the song of the nightingale at various stops in the Caribbean. Nightingales are not found in the New World and Hoose believes Columbus was hearing northern mockingbirds with their varied repertoire.

In 1712, the English naturalist Mark Catesby visited North America and painted 220 species of plants and animals. His paintings included what he called the mock-bird.

Who knew Thomas Jefferson was a mockingbird fan? He had a number of these birds as pets.

The early 19th century was a heyday for American ornithology with the work of Audubon and Alexander Wilson. We learn of their interests in the mockingbird.

We discover more about the inspiration of northern mockingbirds for songwriters and novelists, and about the role that mockingbirds played in bird conservation.

The book is lavishly illustrated with many photos of birds, people and related objects. I learned much from this delightful book.

Herb Wilson taught ornithology and other biology courses at Colby College. He welcomes reader comments and questions at whwilson@colby.edu