Virtually all of Gerald Durrell's work, from "Overloaded Ark" to "Family and Fauna" and a dozen popular books in between, expresses his concern that "the world and its wildlife is being . . . edged into oblivion by our rapaciousness." Long before there was a vigorous environmental movement, in fact, people like Durrell were devoting their lives to reversing the trend of extinction and exploitation. Besides being a writer, he is, as his many readers know, the founder of a private wildlife preserve on the Isle of Jersey, where researchers are attempting to save endangered species by breeding them in captivity.

But "The Mockery Bird" is a novel about a fictional creature, written "in a lighthearted vein," as Durrell says, though still meant to convey his message of conservation and compassion.

The scene is Zenkali, a mythical island paradise lying "on the imaginary line where the waters of the Indian and Pacific Ocean meet and merge." Ruled by benevolent King Tamalawala Umber the Third--irreverently called "Kingy" by everyone--Zenkali is nearing independence from colonial rule.

But the British want Zenkali for a strategic airstrip and military port, a project that would flood a wilderness valley for hydroelectricity and inundate the island with thousands of soldiers and the delights of civilization. Zenkalis are divided over the price of this "progress."

Enter 28-year-old Peter Foxglove, sent by his pompous and venal uncle, Sir Osbert, to assist Kingy's political adviser. Peter falls in love with beautiful Zenkali and with beautiful Audrey Damien, whose father runs the local newspaper.

When Peter and Audrey go camping they accidentally discover a colony of mockery birds, long believed extinct, living in the valley about to be flooded. The discovery causes pandemonium. An international brigade of obnoxious wildlife defenders arrives to Save the Mockery Birds, as Looja--Zenkali's maleficent minister of development (in cahoots with Sir Osbert)--plans to shoot the birds and burn the valley.

Meanwhile, the Fangoua tribe, which considers the mockery bird its god, attacks the Ginkas, who don't, battling it out at Zenkali's English Club, terrorizing the island's dotty British residents. Actually, almost everyone in this book is dotty or pixilated.

There's Rev. Judith Longnecker, a missionary from Ploughkeepsie, Va., who studies guerrilla warfare and concocts stink bombs; Droom, a repulsive scientist, who establishes the exquisite symbiosis between the mockery birds and the Amela tree, Zenkali's only source of income; and Hannibal Oliphant, Kingy's irascible adviser, who surrounds himself with dogs--"A bulldog, a Dalmatian, an Irish Wolfhound, two Pekinese, four King Charles spaniels and a colossal Tibetan mastiff."

And all the characters drink interminably. Durrell always has someone "taking a long pull at his drink," or pouring, gulping, sipping, and draining "another whiskey, bigger than the first." Peter, faced with a crisis, "broke out in a cold sweat at the thought and poured himself another drink." Given the booze and the tropical sun it's a wonder anybody can see the mockery birds, much less save them.

Durrell is an accomplished writer, but he floods us with so many screwballs and antics that the reader--not the valley--is finally deluged, awash in contrived slapstick and stereotypes:

Captain Pappas, who ferries the island's supplies, not only reeks of garlic and has a "goldmine of teeth," but he speaks with "Greek envy in his voice." Audrey's father, Simon, is a "mad Irishman" who, of course, drinks prodigiously.

The native Zenkalis are all simple, grinning, good-natured souls who jabber in pidgin English ("Masa go come with me") except for Kingy--"six foot four . . . built like a huge, chocolate-colored Shire horse"--who speaks impeccably, a graduate of Eton and the London School of Economics. And it's damned embarrassing when Durrell says that the natives "danced with the boneless elegance that can only be achieved by someone with a dark skin."

Durrell's previous books make us care about animals and people. But here the animals are mythical and the people forgettable, like characters in a TV sitcom, which they resemble. He even ends with a commercial, a "tailpiece," that eloquently asks for contributions to his Jersey Wildlife Preservation Trust, pleading "on behalf of these plants and creatures because they cannot plead for themselves."

Given Durrell's stature, such a request is appropriate. But "The Mockery Bird" isn't. It will make some readers laugh, but it won't make them think. And that's a waste of Durrell's considerable talent and a dilution of his important work.