“A behavioral observation will also help. A passing raptor will notice a group of people standing on a mountaintop all looking its way. An accipiter that must drop a shoulder or turn its body to study the crowd is a Sharp-shinned Hawk. A Cooper’s Hawk simply swivels its head, like a turtle looking back over its shell. The body stays firm.”

The quote is from Hawks in Flight by Pete Dunne, David Sibley, and Clay Sutton (Houghton Mifflin, $9.95, paper), a book described as the first holistic birding guide. Moving well beyond such prosaic field marks as eye rings, wing bars, and tail bands, Hawks in Flight gathers field-identification clues from shape, proportion, and behavior–collecting information gained by thousands of birders in more than 50 years of hawk watching.

Hawk watching is a very specialized form of birding. Most birding outings involve wandering through field and woods, walking with a sort of museum shuffle while staying alert for sound and movement. Hawk watchers stand still. They pick out a likely place and spend the whole day camped on it, waiting for migrating hawks to go by.

Watching warblers and other small songbirds, you often sight in on birds that are just a few feet away. You need to know how close your binoculars can focus. Can they render a sharp image of a bird just a few feet from being close enough to identify with the naked eye?

Hawk watching requires identifying birds from quite a long way off. Some will pass so high overhead that they can’t even be seen with the naked eye. Others will fly by hundreds of yards to left or right, mere specks on the horizon.

Hawk watching as semiorganized sport began in the 30s. Hawk watchers gathered at places such as Hawk Mountain, Pennsylvania, Cape May, New Jersey, and Duluth, Minnesota, to monitor the passing of the raptors in spring and fall. These places are choice for geographic reasons. They offer excellent updrafts or provide a route around broad expanses of open water that raptors are reluctant to cross.

Hanging out all day in the same places, kibitzing when no birds flew by, competing to see who could be the first to nail down the identity of a distant dot on the horizon, the hawk watchers began to discover shortcomings in Roger Tory Peterson’s system of identifying birds by noting a few critical field marks–almost always details of plumage color and pattern–that set each species apart.

For example, Peterson suggests using the width of the white bands on tails to separate broad-winged hawks and red-shouldered hawks. The bands are wide on broad-wings and narrow on red-shoulders. This is an excellent mark if the bird is more or less directly overhead. But what if you are standing on a mountaintop watching passing birds a quarter of a mile away and right at eye level?

Hawks in Flight suggests noting the attitude of the wings. Broad-wings hold theirs flat and horizontal; red-shoulders “typically soar on wings that have a slight downward droop, as if the bird were cupping the air.”

Wing shape is another guide. Red-shouldered hawks’ wings are like “a long, rectangular plank. The entire wing juts forward when the bird is in a full soar, as if it were reaching out, arms wide, to embrace something.” In contrast, the broad-winged hawk has short, broad wings that it holds at “an almost perfect right-angle to the body.”

I first encountered the term “holistic birding” at the American Birding Association convention in Tucson in 1986, during a seminar on identifying sparrows given by a brilliant field birder named Kenn Kaufmann. Kaufmann was showing us slides of various species: white-throated sparrows and grasshopper sparrows, Cassin’s sparrows and LeConte’s sparrows. Most of us, good students of Roger Tory Peterson, looked at the slides and started ticking off the field marks–the crown stripes, eyebrow stripes, breast streaks, and patches of ochre on the nape that set each species apart.

Kaufmann kept telling us not to do that. That analytic style is first-level birding, a way to extract some coherence from the overwhelming impression created by a living bird caught for the moment in the figure-eight field of a pair of binoculars.

Holistic birding is synthetic rather than analytic. Kaufmann wanted us to start by identifying a bird’s genus. The experienced eye can do this with sparrows, relying on clues provided by overall shape and proportion rather than details of the plumage. Birds of the genus Zonotrichia–white-crowned, white-throated, and Harris’s sparrows–have heads with high, rounded crowns, clearly defined necks, and breasts almost as bluff in the bow as a robin’s. Ammodra-mus birds–grasshopper sparrows and LeConte’s sparrows–have big, flat heads and the sort of no-neck look common among linebackers.

If you have never tried birding, you probably couldn’t notice these differences. I could show them to you in pictures or on a cooperative wild bird that would stay in plain sight for a long time, but the first time you tried to see them on your own, you’d go crazy. Birds move around. They crane their necks to see or scrunch down to avoid being seen. Their feathers blow in the wind. Flat heads become round heads. No-necks become swanlike. But with experience, you can sort these things out, recognize an unusual posture for what it is, and, as Plato might have put it, see the real shape of the bird under the passing show of appearance.

Pete Dunne, who is responsible for the text of Hawks in Flight, describes holistic birding as “a refined blend of identification skills and conjecture.” The conjecture part of that blend troubles the people who hew to the other school of contemporary birding. This is the feather-by-feather approach, looking at wild birds the way a taxonomist in a museum would look at a dead specimen.

Feather-by-feather birding requires cooperative birds that will hold still long enough for an observer to, for example, study each feather in the middle row of upper wing coverts to determine the shape and extent of the buffy bands at the feather tips. It also requires that the birder be rich enough to own a pair of Zeiss binoculars and a Questar astronomical telescope modified for terrestrial use. Only the best optics are up to the demands of this sort of birding.

Chances are a migrating hawk will not give you the opportunity to make that kind of study. For this kind of bird watching, it’s holism or nothing.

Hawks in Flight certainly provides everything in the world you need to know about watching birds of prey. Imagine a 250-page book devoted exclusively to the field identification of 23 species of birds. My battered old 1947 edition of Peterson covers more than ten times that many species in just 290 pages.

Hawks in Flight is divided into two sections. The first 167 pages feature Dunne’s text illustrated with black-and-white drawings by Sibley. The second section is all photographs by Sutton and others, also in black and white.

The lack of color is deliberate. Looking at distant birds against the sky, you will see everything in shades of gray, so that is the way the book presents the birds.

At one point Dunne writes that this book is not really a field guide. The relaxed narrative of the text is meant to be read at home before you go out looking for hawks. The idea is to prepare your mind for the task, to get you thinking about the sorts of details you will have to notice in order to successfully identify distant birds of prey. The best way to absorb this observational skill is by birding with an expert. If you’ve got no experts handy, Dunne et al are excellent substitutes.

As I said, at first you won’t really be able to apply this knowledge. The birds will insist on being their ambiguous selves. The same bird will sometimes look like a red-shouldered hawk, sometimes look like a broad-winged hawk, and sometimes look like a goshawk. In fact, it may look like all three at once.

But with experience, the scales will begin to fall from your eyes. When the “quick, snappy, hurried” wing beats of the sharp-shinned hawk and the “arthritic” wing flaps of the Cooper’s hawk are personal visual memories rather than words on paper, you’ll be birding at the second level; you’ll be a holistic bird watcher.