As darkness fell last night, U.S. and Virginia agricultural agents entered an Alexandria warehouse to begin killing about 1,000 exotic birds in the name of protecting the American chicken.

A network television crew showed up to film the dozen workers as they donned white smocks and surgical gloves in the parking lot of Smith's Exotic Aviaries Inc. before entering the warehouse -- now under U.S. quarantine -- to kill some 50 species of exotic birds with gas and injections.

"if they'd a been pigs, nobody would care a bit," said one of the agents, acknowledging that four days of publicity about the impending killings had aroused sympathy among the public.

The birds, from parakeets to rare cockatiels, some valued at more than $1,000 apiece, were condemned because oftheir exposure to exotic Newcastle disease. The virus that causes the disease is not hazardous to humans but has the potential to devastate America's $14 billion-a-year poultry industry.

The killings were delayed until last night by a bitter standoff between the U.S. Agriculture Department and 19-year-old Kevin Smith, the largest wholesaler of exotic birds in the mid-Atlantic states, over how much Smith is to be compensated.

The sacrifice of the birds will cost taxpayers $54,000 in compensation, according to Smith, who said he had sought $74,000. But it will not end the threat of the disease to U.S. poultry.

Agriculture officials said they were concerned that Newcastle disease -- which resulted in the deaths of 12 million chickens during a California outbreak in 1971 -- may have been spread to other parts of the country by birds Smith sold before the quarantine was imposed.

"we'll have to track them all down," said an Agriculture spokesman who could not estimate the number of suspect birds but said vouchers obtained from Smith's warehouse indicated shipments went to at least 58 stores in six states.

Agriculture officials said they were not happy at having to kill some of the world's most beautiful winged creatures.

"the USDA has been made to look like a bunch of bumpkins," said Dr. Jerry Mason, the veterinarian in charge of all Agriculture Department task forces. "you don't know how many hundreds of phone calls I've gotten from people saying, how can we stop you from killing those poor little birds?"

Bird entrepreneur Smith maintained from the beginning that the "depopulation," as agriculture officials term it, was unnecessary. Last night he complained that a team of negotiators hired by the Agriculture Department to set compensation prices had undervalued some of his birds, particularly four pairs of cockatoos.

"they figure there's nothing we can do. Every day we wait we're losing money," said Smith who began his business four years ago from his Herndon home and has been called the boy wonder of the bird business.

The birds -- who got the worst deal of all -- were being rounded up last night. The smaller varieties were then placed in plastic bags into which carbon dioxide was pumped. The larger birds were killed by injections of a chemical. Both methods were called humane and said to induce sleep before death.

The killings were continuing early today.

According to world wildlife groups, Smith's birds -- most of them captured in the wilds of South or Central America, Australia or Asia, were lucky to have survived as long as they did.

"the mortality rate in the bird business is absolutely horrendous," said Lewis Reenstein, vice president of the Fund for Animals, which has a worldwide membership of 200,000. "nobody knows for sure, but probably 10 to 15 birds die for each one that makes it to a pet shop."

"hogwash," responds Marshall Meyers, general counsel for the International Bird Institute, which claims to represent most of this country's large wholesalers and importers of exotic birds. "there is a lot of emotionalism on both sides. One can play with those figures," said Meters, who claims that wildlife groups -- which he calls "humaniacs" -- are confusing ligitimate importers with international smugglers whose mortality rates are notorious.

The increasing popularity of exotic birds as pets, spurred on, say store owners, by television shows like "baretta," which features a sulphur-crested cockatoo in a supporting role, has more than tripled prices for some birds in the last five years. Cockatiels and cockatoos sell for a minimum of $1,000. A few years ago a pair of Hyacinth Macaws sold in Los Angeles for $25,000.

That popularity also has spawned a smuggling market. Along the Mexican border customs officials regularly find parrots packed in suitcases, taped to people's bodies, even wrapped and hidden inside hubcaps.

Ken Berlin, a Justice Department lawyer who is heading a six-month-old national task force to prosecute wildlife smugglers, estimates that between 500,000 and 1 million exotic birds are smuggled into the United States annually. The great majority of those birds, said Berlin, were imported under falsified papers by large scale criminal elements.

Agriculture officials maintain that the 19 yellow-naped Amazon parrots that exposed Smith's flock to exotic Newcastle disease were smuggled into this country.

Smith does not argue the point, but says that when he bought the birds he assumed they had been through the 30-day quarantine required by U.S. law. The Los Angeles dealer from whom he bought the birds still was on Agriculture's approved list of privately-owned quarantine stations.

Agriculture officials are skeptical of Smith, but, according to spokesman Dave Goodman, "we can't prove anything so we have to treat him as innocent."

Smith says the officials are trying to shift the responsibility away from themselves, but maintains that criticism does not bother him.

"there's a lot of back-stabbing in the bird business," said Smith. "a lot of it is jealousy," he said.