In 1934 Roger Tory Peterson was turned down by nine publishers before Houghton Mifflin accepted his tiny field guide to the birds of eastern North America. A Field Guide to the Birds was oriented exclusively toward an audience interested in field identification, and nobody knew if that audience was large enough to support even one book.

Peterson’s genius lay in the suppression of detail. You would learn almost nothing about nests or eggs. You would not be told of plumage differences that could be detected only on birds held in the hand. The paintings would show you a stripped-down, schematized version of the bird that would, in almost every case, lead you to a correct identification of anything you were likely to see in eastern North America. And that was the book’s sole purpose.

Like James Naismith, Peterson invented a sport. People in growing numbers got into it, identifying wild birds in the field as a game, an opportunity to display and expand your skills. Many who developed their skills to a very high level used those skills for scientific purposes, but some just birded because it was a lot of fun.

Both the scientists and the fun seekers soon carried a Peterson around in their heads, but they still found themselves occasionally stymied by ambiguous birds in the field. They needed more information, and they bought any book that promised to provide it. As this audience developed, the books got more and more complex–returning to the detailed, feather-by-feather descriptions that Peterson’s innovation had replaced.

In 1983 the National Geographic Society brought out a 464-page guide to all the birds in North America. The same year, Knopf published a three-volume Audubon Society Master Guide to Birding. Both books offered more detailed information about plumage, configuration, and shape than any of their predecessors, but they did it at the cost of portability. The Master Guide to Birding weighs several pounds; it is a book to consult before and after birding trips, not during one.

In 1988 Houghton Mifflin published Hawks in Flight by Pete Dunne, David Sibley, and Clay Sutton. This is a book that treats only one order of birds and shows them only in flight. It is, more than anything, a guide for use in places like Hawk Mountain, Pennsylvania, or Duluth, Minnesota, places where topography and prevailing winds combine to concentrate large numbers of hawks and eagles in a very small space. On a good day birders can count thousands of migrating raptors in that space. With Hawks in Flight to help them, they can identify nearly everything they see, even birds that pass by at very great distances.

Kenn Kaufman wrote Advanced Birding in 1990. He focused on the difficult cases–the immature gulls, the flycatchers, the shorebirds, the groups of species that can drive you crazy in the field.

Now Houghton Mifflin has published what is, so far, the ultimate in specialization. A Field Guide to Warblers of North America describes 60 species belonging to a single family, the Parulidae, or subfamily, the Parulinae (ornithologists waver in their opinion of the exact status of the group). The book is 656 pages long–including a 25-page bibliography. It contains paintings of every plumage of every species known to nest north of Mexico: juvenile, first fall male, first fall female, first spring male, second spring male and female, fall immature, etc, etc. Some species have 11 different plumages. More than 250 separate paintings elucidate every eyebrow stripe, breast streak, and wing bar of both sexes at all ages. If you had never tried birding before, this book would terrify you. You could imagine spending your whole life just mastering this one family. You could imagine that it would take several lifetimes to learn every bird likely to pass through Illinois, and we are but one state among 50. This is a book that should be hidden from novices. Only when you are reliably hooked can you be trusted with so much information about such a small number of birds.

Warblers was written by Jon Dunn and Kimball Garrett, both scientists who are also very well known and respected birders. The excellent paintings are by Thomas Schultz and Cindy House. The project took ten years from first idea to finished product. The two authors examined more than 10,000 preserved specimens of warblers at museums from the Smithsonian to the Natural History Museum of Los Angeles County, and they drew on the expertise of scientists from all over the continent.

Each species gets an extended treatment that includes a brief introduction, a general description, an account of similar species, a discussion of songs and calls, behavior, habitat, distribution, conservation status, subspecies, taxonomic relationships, plumages and molts, and a short list of references. Color photographs supplement the text. The range maps for each species are the most detailed I’ve ever seen. They even include the disjunct populations that live beyond the boundaries of a species’s main range.

It is easy to get interested in warblers. They are among our most brightly colored and strongly patterned birds. They are all small–some are less than five inches long, and only one species is longer than six inches. Your average wood warbler weighs ten grams or less, yet many of these tiny animals make annual migrations from Canada to Colombia and back, in some cases flying hundreds of miles over the open sea during the trip.

In May, when the weather is just right, we get warbler waves, days when the birds are dripping from the trees like rain. Yellow and black are the family’s favorite shades, arranged in sharply defined patterns decorated with chestnut, orange, buff, and blue.

Warblers have picked up a reputation as a difficult group to identify. It is true that there are a lot of them. We see 36 species here in a typical migration season. Also they are small, and they hang out in dense foliage, where it is hard to get a look at them. But if you can see a spring male clearly you can identify it. In almost all cases the markings are quite distinctive. And they often sing during migration, so if you know their songs you can recognize warblers without ever seeing one.

Seeing one clearly is sometimes impossible. The frustrated birder often trains his binoculars on a bird high in a tree and sees nothing but the ass end, the bird’s underparts from behind the legs to the tip of the tail. Warblers makes the first attempt I know of to deal with this problem–there are two pages of paintings of warbler butts. Each picture shows the undertail coverts–the feathers on the rearmost part of the belly–and the underside of the tail. You can check the color and pattern of the undertail coverts, the markings on the underside of the tail, and the length the tail extends beyond the body. You can’t always get a definitive identification from this evidence, but if you learn the details you may be right often enough to impress your friends.

Fall migration presents more difficulties. Adults and that year’s young are all passing through. Each has a distinctive plumage, but the distinctions are much subtler than in spring. Even if you get a good look at the bird you may not be able to name it.

This book will certainly help you with any problem birds you might run into. It is filled with details about how individuals of one species sometimes look like another species, and the sections on behavior and habitat provide yet more clues to identification.

Of course, you can reliably identify 98 percent of the birds you see with the information contained in Peterson, but plainly there are birders out there who regard 98 percent as unsatisfactory. For them this book is essential. It is certainly not a field guide, unless you can afford to hire a book bearer to accompany you on birding outings. It is primarily a reference book, a work to consult after a field trip. You can compare your field notes with the pictures and descriptions and probably learn something you didn’t know before.

If you are a casual birder or only just getting into the game, you won’t need this book for some time. Study your Peterson and get out as often as you can. When you begin to get really interested in the uncertain cases, you will be ready for A Field Guide to Warblers of North America.