IT IS ONE OF THE SUBLIMEST THRILLS nature offers, to see a shape flitting through the branches (""a very tiny, slender mite, smaller even than a Chicadee, blue-gray above and whitish below . . .''), hear a call (""a thin peevish zpee'') and, paging frantically through the more than 700 species and subspecies listed in ""A Field Guide to the Birds,'' finding that this description precisely matches that of the blue-gray gnatcatcher. A bird, a wild creature, subject to no human laws, grubbing out a meager living from bugs that not even most other birds would bother eating, somehow manages to turn out looking just like Roger Tory Peterson painted him. How did it know?
Peterson, who died last week at the age of 87, was many things: author, illustrator, naturalist, photographer and lecturer. But he will be remembered best for his obsessive lifelong effort to put birds, figuratively, within reach of every American. His two main field guides, covering birds in the Eastern and Western halves of the nation, have sold more than 7 million copies since the 1930s. His was not so much a scientific quest as an effort to compensate for the fact that nature fails to equip wild animals with labels. Before Peterson, birders had to rely on reference works that -- owing to their own size and weight, and the obscure anatomical differences they used to differentiate similar species -- were most useful if you shot the bird first. Peterson was among the first to grasp the potential for a book that would help people identify birds while they were still alive. When Peterson describes the voice of the short-eared owl as ""an emphatic sneezy bark, kee-yow!'' you can bet your life that if a bird hoots, sighs, moans or chirps, it's, well, something else.
Because Peterson never lost sight of the goal that sends people into bug-ridden woods, trash-strewn garbage dumps and frozen marshes at dawn, which is to see more birds than anyone else. His own life list stood at approximately 4,700 species, glimpsed, or at least heard, on all seven continents, out of a theoretical worldwide total of approximately 9,000. In 1980, it was said, he was one of only two people in the world to have seen all 17 species of penguins. He traveled to the remote woods of Louisiana and saw the ivory-billed woodpecker, which, its immortality thus ensured, soon thereafter went extinct. He has seen the Connecticut warbler, which sounds like no big deal for someone who lives in Connecticut, until you try to tell it apart from the mourning warbler. A careful reader of Peterson's chapter on ""Confusing Fall Warblers'' will know that the difference between these two birds is that one has a white ring around its eye, and the other has a white ring that goes most of the way around its eye.
At the age of 72, as a fund-raising stunt for the National Audubon Society, Peterson counted 179 different species in 24 hours of nonstop birding in the Big Thicket in east Texas. That same year, he finally saw the lesser prairie chicken, which was the last resident North American species to elude him in six decades of birding, and it wasn't even that exciting. ""Once, I would have been excited,'' he said. ""But I've read and taught so much about the lesser prairie chicken that I wasn't at all surprised when it showed up.''
Although Peterson's Field Guides continue to sell well, they now have competition from a new generation of bird books with photographs of birds in their habitat, which is fine if you want to appreciate nature in all its riotous profusion of rippling water and leaf, light and shadow. But if your aim is to make good and sure the bird you're looking at is a vesper sparrow and not a Savannah, there is no substitute for Peterson's drawings, with their single-minded commitment to illustrating what birds ought to look like. Now that he's gone, how will even they know?