AMONG the quainter customs of the Manhattan species of bird are the mid-winter migrations which might be called the Who He? Hols. On a gelid weekend in January, New Yorkers are required to clear out of town, heavy-laden with satchels, down-filled anoraks and truckloads of office work. They head North, car roofs bulging with luggage, only to return on Monday night, bruised, proud, and snuffling, having opened not a one of the spine-buckling cases of office work they had dragged along, but having consumed several stone-worth of the fudge and apple butter they had trundled back with them. The occasion for the frosty holidays, it is thought, is to honour the birthdays/assassination dates of several premier American historical figures, which may include Martin Luther King, Abraham Lincoln, Paul Bunyan, Jimmy Hoffa and George Washington. In much of the country, this august purpose is accomplished without leaving off work, but New Yorkers' awe of this nation's Great Men is such that they skip the office in order to allow time for undistracted contemplation.

Since the holiday falls only two weeks after New Year's, it has a way of rushing up at a Manhattanite in the alarming manner of a massive chairlift- supporting beam beneath a particularly tricky ski-jump. Usually it is not until traffic starts building late on the Thursday of the festival weekend that New Yorkers realise that the free Monday has skidded back onto the schedule, which leaves them only a few hours to find a suitably exorbitant rustic bed and breakfast to receive them before the rumour goes round that they have no getaway plans. By the time the bookings rush begins, all flights to anyplace clement have been filled by the sort of people who plan ahead, which includes midwesterners, coupon-clippers and residents of university towns, but emphatically not New Yorkers. Therefore, New Yorkers are forced to head for the snow-capped hills, covered bridges and white clapboard houses of rural New England. Last-minute weekenders make phonecall after phonecall, trying to book rooms that cost at least $150 a night, inns that serve venison en croute and hire cars with the steel-studded tyres that stand a chance on glare ice. It is an exhausting procedure, but far less painful than the prospect of having no photos to swap with officemates at the coffee urn the following week, or, worse, no dramatic ice-borne injuries to flaunt.

They go, most of them, to Vermont, Maine and New Hampshire, to places where the chief source of local protein is fish, tugged up through a hole in the lake in an ice-fishing shed, and where the only other food source available is gift shop souvenirs - fudge, honey mustard, and grainy, sickly- sweet maple sugar candy. It is preferable to ski or travel by horse-drawn sleigh during the outing, but all that is strictly required is to go someplace colder than Manhattan, that offers a reasonable danger of severe blizzard. Since there is not enough snowcovered ground on the eastern seaboard to accommodate every New Yorker who wishes to hurtle down it on a snowboard, some must make do with skidding down icy, precipitous hills in their automobiles. Losing a hire car in an ice-crusted country roadside slushpit is considered roughly equivalent to skiing the double-diamond slopes on Stratton in terms of bragging rights, and also occasionally allows for the stylish wintersports souvenir of a full-leg cast. When New England gets full up, New Yorkers keep driving until they find someone in Canada who will take them in. Not everyone can be accommodated even in Canada, so those who feel their exclusion most keenly bite their lips and vow not to be caught out at the next Who-He? Hol - the President's Day break in mid February.