Roger Tory Peterson died July 29. There was no one else like him while he was alive, and no one like him is apt to come along.

If there is anyone we can compare him with it is the great artist– ornithologists of the 18th and 19th centuries. The list of such men is short. It starts with Mark Catesby, who visited the southern colonies and the Bahamas in the 1730s and ’40s. Alexander Wilson is the next great figure in this line, and John James Audubon is the culmination of the type.

These men were explorers. Each of them found species unknown to European science, and their books were both a way to make the scientific world aware of these new finds and a way to pay for the expeditions that found them.

By the time Peterson’s first Field Guide to the Birds was published in 1934, scientists had pretty well delineated North America’s avifauna. Peterson directed his work to a nonscientific audience, and thanks to modern printing methods–which could reproduce paintings in full color–his field guides were accessible to an audience much poorer than the genteel amateurs of the natural sciences who had supported Audubon’s efforts. Teenage boys could afford a Peterson.

Wilson and Audubon were both scientists and popularizers. Peterson was a popularizer whose contribution to science was more indirect. His books helped teach generations of scientists how to identify free-flying birds in the field, and that skill helped make their contributions possible.

Peterson led an enviable life. He grew up in Jamestown, New York, at the extreme western end of the state. His childhood interests were birds and art, and in his adult life he became rich, famous, and widely admired by pursuing those interests. He left his hometown to study at the Art Student League and Cooper Union in New York City. In New York he hooked up with a small group of teenage bird nuts who called themselves the Bronx Bird Club. The membership included several young men who went on to notable careers in ornithology, including Joseph Hickey, who became a professor at the University of Wisconsin, and Alan Cruickshank, who was associated with the American Museum of Natural History.

Peterson was teaching at a high school in Massachusetts when he completed A Field Guide to the Birds of Eastern North America in 1934. It was a skimpy work by today’s standards. Many of the plates were in black and white, and the color plates squeezed as many as 15 species onto one seven-by-four-and-a-half-inch page. Four publishers turned down the book before Houghton Mifflin decided to take a chance on an edition of 2,000 copies. That edition sold out within two weeks, and the subsequent editions of the work have been doing a brisk business ever since.

Peterson’s genius lay in a rigorous suppression of detail. His birds were schematized, stripped to essentials. He invented a system of identification that selected two or three features of each species as the field marks that set that species apart from similar birds. These field marks were highlighted in the paintings with straight lines that served as pointers. Anything that was not absolutely required was left out.

My favorite bird from Peterson’s early period is the male canvasback duck. A real live canvasback seen in good light has a dark gray beak, a rusty-red head and neck, and a black breast. Most of its body is white. Its wings are white tinged with gray, and its hind parts are black.

Peterson renders the swimming bird in black and white as four almost featureless solid blocks. The beak and the head and neck are gray, with the beak slightly darker than the head. Below that is a solid black block representing the breast. Another black block at the rear shows the tail. The body and wings are a simple expanse of white with no demarcation of folded wings from body. In fact, the bird apparently has no wings.

I can testify that this minimalist rendering works in the field. I identified the first canvasback I ever saw with the aid of Peterson’s painting.

It has been said that Peterson’s paintings were a perfect fit for the optics available in the 30s. Most birders were using four- to six-power binoculars of somewhat less than astronomical quality. On a gray morning a distant canvasback sitting on a lake, perceived through those binoculars, would look very much like Peterson’s schematic painting.

If you want to succeed you need to be in touch with the zeitgeist, and Roger Tory Peterson was. His book not only sold well, it founded an industry. Look in any of today’s bookstores and you will find shelves full of field guides to birds, mammals, reptiles, insects, mushrooms, trees, wildflowers, fossils, rocks and minerals, and everything else under the sun. And thanks to star guides, everything beyond the sun as well.

Most Americans grow up in the city or suburbs, where nature is a distant rumor. Our grandfathers tend to know more about accounting or plumbing than they do about scarlet tanager nests. Field guides are the way we learn about nature, and Roger Tory Peterson was the best field-guide creator ever. Almost all of those shelves full of guides feature works done by committee. Except for Peterson’s, the bird guides all have several fathers. The National Geographic Society’s Field Guide to the Birds of North America doesn’t even have an author’s name on the cover. Inside you can find a list of more than 50 editors, researchers, writers, and artists who contributed to the work. They remind me of the armies of presidential speechwriters who labor mightily to produce stuff that is not as good as the speeches Lincoln wrote for himself.

Peterson’s work earned him just the right degree of fame.

Fame is a very tricky commodity in contemporary America. People who have too much, people who are, for example, known to both Sam Donaldson and John Tesh, can get caught up in nightmarish existences. They simultaneously live their own lives and the lives of fictional characters loosely based on them. Peterson was known and admired by a relatively small group. They loved him, but they wouldn’t be inclined to tear his clothes off or steal his garbage before it was picked up.

I had the privilege of going birding with Roger Tory Peterson at an American Birding Association convention ten years ago. He was enjoying his ideal degree of fame at the convention. He was surrounded by intelligent, knowledgeable people who held him in great esteem. He could bask in the glow of their admiration and still know that if he left the hotel and walked into a 7-Eleven just down the street he would be just another elderly gent.

On the field trip that we shared with about 20 other people he was just another birder. A very good birder, but only one of several very good birders. His interest then was in seeing birds and enjoying the fellowship of other people who also liked looking at birds. He was obviously not thinking too much about being the famous Roger Tory Peterson.

The doors that Peterson’s books opened have enriched the lives of millions of people, and they have made a significant contribution to the protection of the environment.

It was birders armed with Peterson’s who first noticed the decline in bald eagle numbers that followed the introduction of DDT. Many of the tall-grass-prairie remnants around Chicago were discovered by people using his guide to wildflowers. More broadly, he helped people realize what was at stake in the environmental struggle. You can’t care about something if you don’t know it exists, and Peterson’s books made it possible for us to care. He is irreplaceable.