'I ticked a tawny yesterday'

''WE'RE going twitching. Like to come along?'' During my stay as a voluntary warden on a British bird reserve I grew to dread this question. What obscure sewage pond or inaccessible rocky spit would my fellow ''vols'' head for this time in their never-ending quest for a new bird?

''There's a royal tern reported at Cley up in Norfolk.''

I had no delusions that we would in fact see the bird. What faith I'd ever had in these phantoms winging their way through the twitching grapevine had long since vanished. Each time a rare bird was rumored to have been spotted within a hundred miles of our reserve, my friends would pile their scopes in the trunk and careen down one-lane roads at terrifying speeds. Each time they would return home with the bemused and faintly bewildered air of troops after an indecisive battle.

Still, there was something noble about their unwavering expectation that next time they would see the bird. Their magnificent ability to hope impressed me. As we set off for Norfolk, I found my pessimism softening. Perhaps this time. . . .

The royal tern was not there, although we tramped five miles with heavy scopes on our shoulders to confirm this. As we tramped back to the car I had plenty of time to reflect upon the essential differences between my companions' approach to bird watching and my own. The issue, I decided, was one of classification: They were twitchers, and I was a birder.

There are an astonishing number of twitchers in England (and elsewhere, too, although ''twitcher'' seems to be a peculiarly British term) who will do almost anything to see a bird they have not seen before. (I was told that the word derived from a well-known birder who became so excited every time he spotted a rarity that parts of his body began to jerk restively.)

A birder packs up binoculars, lunch, and field guide in a rucksack, strolls along a well-marked trail, sits serenely in a bird blind, and comes home in the afternoon for a cup of hot tea. A twitcher hears a rumor that a Siberian rubythroat has been sighted on the Shetland Isles, takes the day off, leaps into his car, catches the next boat or plane there, and camps out under some baffled farmer's hedge for several days - along with 200 or so other twitchers. The relationship between birders and twitchers is analogous to that between those who ''like horses'' and owners of Kentucky Derby hopefuls. Birders ''like birds.'' Twitchers are out to win.

Their lingo bespeaks this uncompromising drive. One conversation I overheard went something like this:

Twitcher A: ''Went twitching last night.''

Twitcher B: ''Get anything?''

A: ''Dipped out on the Med. Met some dudes and grocks in the hide who gave me duff gen about a pec.''

B: ''Stringy?''

A: ''Of course. Jizz was all wrong. They need their bins examined.''

B: ''Don't mean to grip you off, but I ticked a tawny yesterday.''

A: ''Really? I flogged and burned up the bush for that last week. Where?''

B: ''In passage - gone now.''

A: ''Good megatick.''

B: ''Quite.''

A rough translation: Two twitchers meet, and the first remarks that he hunted for rare birds the previous night but missed seeing a reported vagrant called a Mediterranean gull. He met some weekend birders and novices in a bird blind who told him that they could see a pectoral sandpiper, but he concluded they were mistaken, since the bird's behavior was uncharacteristic, prompting him to comment on the merits of their binoculars. The second twitcher then mentions that he recently observed a rare bird called a tawny pipit in migration, thus one-upping his colleague, who had previously searched for it extensively but now has little chance of seeing it.

In their zeal to augment their lists of birds ''ticked,'' some twitchers made me wonder whether they were missing the point. But most twitchers, friends included, were capable of joking about their single-mindedness and even appeared to still ''like birds.'' I envied their tenacious optimism, their never-quashed belief that alertness would eventually pay off. They went through life keenly aware of the natural world around them, and with an attitude that any day, at any time, something wonderful could happen.

''Hear there's a little egret near Woodbridge. Want to come?''