Ever since Roger Tory Peterson's arrow first hit the mark 50 years ago, Houghton Mifflin has had a best seller on its hands. But for an accident of publishing, however, this golden jubilee of an American classic - ''A Field Guide to the Birds of the Rockies,'' recently republished in a revised and enlarged edition sporting a flexible white plastic binding - might never have occurred.
When he first submitted his book to Little, Brown in the early 1930s, Peterson tells me in a telephone interview, it was rejected because that publisher already had in the works a guide by Thornton Burgess, with plates from Louis Agassiz Fuertes's ''Birds of New York.'' That, as Peterson notes now, ''would have been my great competition.'' However, he continues, ''the printer did such a bad job that Little, Brown decided not to publish the book after all.'' Meanwhile, Houghton Mifflin had accepted Peterson's guide, which came out in 1934.
It has reaped the benefits ever since. So, to a degree, has the United States. The book has been credited, along with Rachel Carson's ''Silent Spring, '' with stimulating the current widespread movement for ecological awareness and environmental quality control. Why? Because, as Peterson observes, ''birds are a litmus, indicating when something is wrong in the environment.''
There wasn't any real competition for the book until 1966, when Golden Press put out its enormously popular ''Field Guide to the Birds of North America,'' with plates opposite each page of text for easy reference. The next year Peterson published his third edition (the second edition had appeared in 1947). The 1980 edition put plates opposite text, thus meeting the challenge from Golden. Now publisher and author have millions of sales behind them - and, with the fourth edition (384 pp., $11.95) in bookstores, undoubtedly millions ahead in the future.
One of the reasons for this phenomenal publishing success is Peterson's arrow. A simple diagnostic system, it points to the distinguishing feature of a bird, which enables the user to identify quickly what he or she is looking at in the field. The succinct text amplifies the information in the patternistic pictures. The result is a field guide that functions as an introduction for a lot of people who need first to know the name of something and then what it is and does. ''After they learn to identify the components, they go on to see connections,'' Peterson says.
How did Peterson develop this system? He says that when he was a boy he found the few field guides available too complicated and difficult to use. ''I thought they ought to be much more direct,'' he says. ''I read Ernest Thompson Seton's novel of a boy who was in the same predicament. He thought that if you looked carefully at the bird's markings close up you could spot them farther away. That sounded like a good idea, so I tried it and it worked.''
Peterson's perfected ability to spot and clearly describe identifying features of birds prompted his friend William Vogt to suggest that he do a field guide, which would teach others how to know the birds. Peterson had the ability not only to write the text but to do the illustrations as well, having studied at the Art Students League and the National Academy of Design in New York, so he went ahead - and made history.
Bird guides led to a whole series of 30 nature guides which are edited by him and use his diagnostic system.
How does he do all these books, take big blocks of travel time for birding and promotion, and also paint his ''bird portraits,'' which hang in museums and collectors' homes?
''Ten hours of work per day, seven days a week, year after year,'' he replies. His wife, Virginia Marie, adds, ''We read all the literature it is humanly possible to collect - read current articles, books, checklists. We go to the state (Roger is writing about) and talk with local experts for information otherwise unobtainable.'' Peterson confesses that ''very scientific ornithological information is beyond my scope, so I just read the summaries of articles like that.''
Ginny Peterson draws the maps that are the newest addition to the bird guides (obviously in response to competition from the Golden Press guide, which has featured range maps since it first appeared). They are larger and more detailed than the Golden ones, but appear together at the back of the book rather than opposite the plates as in the Golden guide. In this way the publisher can update the maps easily instead of requiring that the whole book be remade.
Peterson begins work on the color plates for the field guides by making drawings on tissue, which are studies of the birds based on what he has seen in the field, stuffed skins, and photographs. When he gets them the way he wants them, he traces the finished drawings onto paper, then paints in watercolor with final detail in acrylics.
His bird portraits are more painterly, free of the constraints of the field guide. They express what the birds mean to this versatile man. He tells of seeing a flicker about four feet off the ground on a tree trunk when he was a boy. ''I thought it was dead,'' he remembers, ''and I touched it. It exploded into life - it was like a resurrection! Ever since, birds have symbolized to me the most vivid expression of life in their mobility, their color, their incisiveness.''
He goes on to note that ''birds are what they are. For instance, the penguin is dedicated to being a penguin. He's not a clown in baggy pants! I like to give birds full respect for what they are. It's a naturalistic, rather than humanistic, approach. The humanistic approach is not quite the truthful one.''
In celebration of the field guide's 50th anniversary, the Smithsonian Institution's Natural History Museum has mounted an exhibition (through Sept. 3) of some original artwork for the plates, and other drawings and paintings by Peterson from various stages of his career. The museum is also showing a videotape that lets you see the bird and hear its song, and at the same time Peterson tells you what its distinguishing marks are.
Peterson's approach has won him the Medal of Freedom, presented by President Carter a few years ago, among many other honors and honorary degrees. This past April, Smithsonian chief S. Dillon Ripley presented him with the institution's highest award, the Smithson medal, which Peterson says he prizes second only to the Medal of Freedom.
There are many festivities this year to celebrate the field guide jubilee, and they cut into Peterson's valuable working time. How does he like that?
''We try to have fun,'' he responds. ''I like to see what the people are like who have the guide. They're such a cross section!''
Bird watching may well lead to people-watching, and no doubt the latter requires the same skills as the former. Whatever the challenge, Peterson has the last word: ''The main thing is to have fun, isn't it?