The sport of bird-watching in America has been shaped largely by the guidebooks birders use to identify what they see. And the guidebooks have, to a considerable extent, been shaped by the kinds of optical equipment available for use in the field.

Until early in this century, the shotgun was the principal tool of bird study. Naturalists of the time had only cumbersome telescopes to work with, and they were investigating a North American avifauna that had only begun to be described. The only sure way to nail down an identification was to shoot the bird and then compare the dead specimen with a detailed account printed in various handbooks of American birds.

These accounts usually started with the beak and worked backward to the tip of the tail, describing the color and pattern of every feather, and noting such details as whether the first primary wing feather was longer than the second and by how much.

Roger Tory Peterson revolutionized the game in 1934 with the publication of A Field Guide to the Birds. Instead of a feather-by-feather description, he relied on a few–rarely more than three–prominent traits, or field marks, to identify a species. His paintings, which illustrated the book, were impressionistic. Instead of precise renderings of every feather, they showed broad areas in solid colors with no details at all. Some, for budget reasons, were printed in black and white.

His rendering of a male canvasback duck is a prime example of his style. He shows the bird as you would see it sitting on the water, and he captures it beautifully with nothing more than five solid shapes in black, gray, and white: a dark gray bill, a medium gray head, a black chest, a white body, and a black rump. The only detail shown in any of these color blocks is the eye.

I can report from experience that this minimalist presentation is quite sufficient to identify the bird if you encounter it in the wild. It is also just right for the four-power or six-power binoculars of modest optical quality that most birders were equipped with in the 30s and 40s. Too much detail would make the job of identification seem harder, and most people wouldn’t be able to see it on the birds anyway.

Things have changed since 1934. The average optical instrument is better, and the best is amazing. Some birders now go into the field with ten-power roof-prism binoculars that provide a sharp, bright, clear image of every barbule on every feather. For long-distance viewing, looking at canvasback ducks sitting well out from shore on Lake Michigan, for example, you can get a Questar reflecting telescope, an astronomical instrument modified for terrestrial use, that will provide extraordinary images at 40 power or above. Birders with Questars also point them at birds at close range, a practice that comes close to establishing a new sport that we could call “feather licing.” How many tiny parasites can you see lurking in the plumage of that solitary vireo?

This fabulous machinery is expensive, of course. The prices of the best binoculars are creeping inexorably toward $1,000, even with discounts, and a Questar with the necessary accessories goes for more than $3,000. Free-lance writers and other such starvelings cannot afford this stuff, but this is the equipment that presently defines the limits of the sport of birding.

The other major change since 1934 is the emergence of large numbers of very experienced and very skillful birders. There are still millions who confine their birding to watching whatever shows up at their backyard feeder, but there are at least tens of thousands–possibly hundreds of thousands–of really dedicated bird-watchers, people who spend almost all their free time birding.

Birders like these, outfitted with the best optical equipment, have no need for patternistic renderings of canvasbacks. They are looking for things such as the article in the new issue of Birding magazine that devotes eight pages of text, photos, paintings, and drawings to the problem of separating the common ground dove from the ruddy ground dove.

Back in 1980, when Dr. Peterson published his completely revised edition of A Field Guide to the Birds (the book covers North American birds east of the Rockies), reviewers in Birding magazine were somewhat less than enthusiastic. They admitted that the book was excellent for beginners. They liked the way it was organized, with text and paintings for each species on facing pages, and they liked the range maps. But they complained that it failed to incorporate a large body of information that birders had amassed through decades of field experience. And they wanted better treatment of such difficult groups as gulls, hawks, and shorebirds.

Now, Houghton Mifflin has published the completely revised third edition of Peterson’s A Field Guide to Western Birds ($15.95, paper), covering all the birds occurring west of the 100th meridian (which, for the geographically impaired, runs more or less through Dodge City, Kansas).

To my mind, this is the best work he has ever done. The text is clear, concise, filled with information, but very readable. The paintings are still somewhat impressionistic, but they are far more detailed than those in the early books. I don’t pretend to have the kind of expertise that can judge whether the bill of the rufous-necked stint has been rendered to perfection, but I think I can say something about art. Roger Tory Peterson has established himself as one of the great American painters of birds, somebody who can be mentioned in the same breath as John James Audubon and Louis Agassiz Fuertes. His birds look ready to fly off the page.

This edition also provides fuller treatment of immature gulls than the eastern book, as well as splendid paintings of hawks in flight. I wish now that Dr. Peterson would go back over the eastern guide and bring it up to this standard.

Houghton Mifflin is also thinking about the needs of expert birders with excellent optical equipment. As part of their Peterson Field Guide Series, which now includes 41 volumes by various authors on practically everything in the universe, they have published A Field Guide to Advanced Birding by Kenn Kaufman ($14.95, paper).

Among serious birders, Kaufman is almost as well-known as Roger Peterson. He started birding at the age of six. At 16, he quit school and went on the road in search of birds. In 1973, after two years of wandering, he did a Big Year, traveling from Florida to Alaska to see as many birds as possible in North America in a calendar year. His total of 671 was a record at the time. And he did his Big Year in such style. His total budget was $1,000, and he did most of his traveling by thumb. These days, the Big Year is a game for people with Gold Cards. One man even had corporate backing.

Kaufman is now an associate editor of American Birds and special consultant to the Philadelphia Academy of Sciences. He learned about birds the way Abe Lincoln learned about the law: not by piling up hours of graduate study, but by doing.

Peterson’s guides can tell you how to identify most birds most of the time, but in a single volume covering hundreds of species there simply isn’t room for the kind of detailed discussion that problem birds require. Kaufman focuses only on the difficult groups–gulls, shorebirds, accipiters, Empidonax flycatchers, and others–the birds that give everybody fits, even the experts.

His text is really a return to the feather-by-feather descriptions that preceded Peterson, only this time the details are provided for people looking at birds through excellent binoculars or spotting scopes rather than for someone holding a bird in his hand.

His treatment of the genus Empidonax is an excellent example of his method. We have 11 species of these small flycatchers in North America. Five are seen regularly around Chicago. To introduce the genus Kaufman says, “They areÉlittle gray birds (tinged with olive, brown, or yellow) with wing bars and eye-rings. Their specific characters are so subtle that there is often more variation within a species than there is between any two species in the genus. Even museum specimens are often difficult to name.”

The only certain way to identify an “empid” is to hear it sing, and the only certain way to find singing birds is to travel to their nesting grounds. According to Kaufman, the close study of singing males is the essential first step in learning about the genus. Working with birds of known species, you can then start studying such things as bill shape, wing-tip shape, the color and pattern of the lower mandible, and the distance the longest primary wing feathers extend beyond the secondary and tertial wing feathers when the wing is folded. After introducing these subtle field marks, Kaufman discusses each empid species individually, applying these marks and noting minute plumage differences that may be useful. He notes the timing of molting for each species, since a bird with new fresh feathers may look quite different from a bird of the same species with old, worn, faded feathers.

Even if you master all these marks, you won’t be able to name every empid you see. As Kaufman says, “If you reach the stage at which you feel you can name every Empid you see in the field, you are probably deluding yourself.” He has examined thousands of museum specimens and studied thousands of birds in the field, and the best he can do, by his own estimate, is name 80 percent of the birds he encounters.

A Field Guide to Advanced Birding, with its intensely detailed discussions of minute differences between similar species, could be a relentlessly tedious experience for its readers. Instead it is consistently pleasurable to read. Kaufman’s warmth and wit come through in his writing, as does his continuing delight in the sport of birding. He never loses sight of the fact that birding is something people do for fun. If fun for you means being able to name every immature gull you see, he will give you the information you need. If fun means listing a whole bunch of different birds simply as “imm. gull sp.,” that’s OK too. It’s your game. You can play it any way you want to.