``Check out that sharp-shinned hawk -- oh, it's a kestrel,'' says Tom Carrolan as he whizzes around a corner on his way to the Crane Wildlife Reservation in North Falmouth. ``When you see a bird hover like that, it's a kestrel.'' We're far into bird migration season again, and woods, hedges, and shores are filled with exotic feathered visitors: shore birds stoking up and resting for the final leg of the trip to their nesting sites in the Arctic, warblers on their way to the fens of Maine and Quebec, merlins headed for the taiga of Canada.
The Massachusetts Audubon Society is celebrating the event with its fourth annual Birdathon.
A Birdathon is a kind of competition. Sanctuaries dispatch teams of birders who attempt to see as many different species as they can in a set 24-hour period. Other people pledge a nickel or a dime or a dollar for each species seen. The proceeds go to the sanctuary.
According to Susan Drennan, editor of American Birds, Birdathons occur in places as far flung as Florida and California, Texas and Michigan, Delaware and Ontario, Canada. They take place, she says, ``over the whole country.''
Migration requires a lot of fuel, and many birds have evolved complex relationships to their food sources, says Mr. Carrolan, organizer of the Birdathon. For instance, the red knot comes to New England and Delaware Bay to feed on horseshoe crab eggs laid about this time.
The expedition starts off at exactly 6 p.m. Friday at the Crane reservation. ``The last thing we want to do is have all six of us see exactly the same birds,'' explains Mr. Carrolan. ``Let's say we all get 150 species of birds, but they're all the same species; what's the point?
``Last year, the winning total was 192; it'll take 180 species to win this year, at least,'' he adds.
Going out with a birder makes you feel as if you have clay in both ears and blinders on your eyes. Delicate twitterings ring you in an invisible circle, and it takes great knowledge to distinguish among them. Listening is as important as watching.
``What was that tweet tweet?'' the novice finally asks.
``No birds go tweet tweet except in Cole Porter songs,'' Carrolan answers with just a trace of sternness.
An invisible squeaking passes directly overhead. ``Goldfinch,'' he mutters.
Some chimney swifts fly by, a group of tiny bombers. ``They're like cigars with wings,'' says Carrolan.
A little more walking and listening. ``There's a nice grasshopper sparrow. They've just arrived. In a few weeks you'll only see two in each area, a male and a female whose territory that is.'' He makes a peculiar kind of whooshing sound, and one sparrow replies.
``You can get the wrong idea about bird watching if you take a Birdathon or a big day as an example. Usually I'd spend time just looking at prairie warblers. This is see it, check it off, and on to something else. It's a little colder and more scientific.''
He focuses the telescope on a meadow lark. Through the lens, what had been a small grayish dot is revealed as a plump and delicate being with a gorgeous vivid yellow breast marked by a deep black vee.
Birds are not only found in sanctuaries. Birders notice them from cars and along the side of the road; and they check out power lines. ``A power line is a long, narrow sandpiper habitat,'' says Carrolan.
Secrecy is the order of the day during a Birdathon, though there was a flap after a Birdathon in New Jersey a few years ago when somebody spotted an extremely rare (for the United States) fork-tailed flycatcher and kept this scoop to himself until the competition was over.
To see many different kinds of birds you have to look in many different kinds of habitats. After birding North Falmouth, Carrolan's team heads off to Wellfleet, on the very tip of Cape Cod.
Another thing, during a Birdathon birders don't get to sleep much. Midnight might find them wandering around a swamp -- the world a blurry black and white -- straining out traffic sounds while listening for screech owls. Then they are up again in the gray-blue dawn, looking for shore birds.
``We're going to see close to 100 species today and we're not exactly super-duper birders,'' says Carrolan as we sit down to a whale-watch breakfast in Provincetown after about three steady hours of birding.
The whale watch is necessary because some birds seldom stray within sight of land. So while all the whale enthusiasts are on the port side of the boat, watching humpbacks breech, spout, and sound, the birders are over on the starboard rail looking at Bonaparte gulls, black-legged kittiwakes, and common terns.
Back ashore, the Beech Forest Trail, part of the Cape Cod National Seashore, is a haven for warblers, tiny colorful birds who move swiftly through the bare branches of the trees. And the warblers are out in force: Tennessee, parula, yellow, magnolia, bay breasted -- 17 kinds in all. There are plenty of other birds there, too -- such as a group of broad-winged hawks, inelegant with their missing tailfeathers, and a rose-breasted grosbeak posed high in a tree with pinkish buds, looking like a Japanese print.
Onward to see migrating shore birds at Audubon's Wellfleet Bay Wildlife Sanctuary. We pass a green-backed heron, poised on a stump in the silver-blue water, composed like a beautiful painting. ``He's called a green back, but there's no green on the back really,'' says sanctuary director Bob Prescott.
In a nearby wooded area, Prescott points out an adolescent great horned owl that has fallen out of its nest. It sits there on a fallen tree, beige feathers fluffed out, like a matron in a fur collar. It opens a small beak petulantly and says ``peeeeeeep'' in a nasal tone.
``I love it. The most ferocious carnivore in North America and its cry is `peeeeeep,' '' says Prescott. ``They're pampered. He's saying to his parents, `Hey, get me a mouse.' ''
The Birdathon ends precisely at 6 p.m. Saturday, and the birders begin arriving with their totals. Later that evening the word comes in: The prizewinning count is 203, a record for the Birdathon. Carrolan describes it as ``a 24-hour snapshot of the migration through New England.''