A bunch of swans are behaving badly in the Chesapeake Bay, according to the local ecologists. Ecologists are a funny species. They try to reduce the public to tears over dangers threatening the lousewort, and then, when you're all soft and misty-eyed, they tell you to hate swans.

It's not going to work. You can't change a swan into an ugly duckling.

Everybody knows that swans have Grace Kelly manners. If they are cutting up, vandalizing the Chesapeake Bay and terrorizing the fishies, theremust be a reason.

The first question is why swans are doing it in the Chesapeake Bay at all, instead of providing foreground interest on travel brochures of castles. The report by the Chesapeake Bay Foundation-Youth Conservation, which blew the whistle on the swans, says the first ones showed up suddenly and "accidentally" in 1962. A pair of swans is supposed to have escaped from captivity on the Eastern Shore, and to have produced 300 descendents, who are now accused of hogging all the underwater vegetation and using the place as a year-round residence instead of migrating to fashionable resorts like the rest of the population.

The answer should be obvious. These birds are under a cruel enchantment. That is the only possible explanation for not getting out of town in the winter if you can afford it.

If the Youth Conservation Corps doesn't mind staying up late, it might try to observe the swans between midnight and dawn. Won't they be surprised when they see a Snow Maiden Corps tripping around the Chesapeake Bay in perfect formation.

The fact is that the swans are taking up unpleasant habits like chewing eelgrass because they are unhappy. And the reason they are unhappy is that they are under an evil spell which forces them to be eelgrass-chewing swans when they really want to be champagne-drinking maidens.

The foundation ominously suggests "taking steps to control their population growth," predicting that otherwise the Bay will have 2,000 to 3,000 swans in a couple of years. Nobody wants that - there are few enough solo parts to go around as it is.

But there is a kinder, simpler solution. The swans may be changed back into maidens if only each can find someone who will swear to love her, marry her and never for an instant love another.

Any Chesapeake Bay fisherman who is concerned about swan damage should be told not to shoot swans or loot their eggs. All he has to do when he sees a swan is to grab it and give it a great big kiss.