Two tons of cracked corn were dropped on Barnegat Bay from a Navy helicopter today in an attempt to prevent thousands of birds from starving.

The corn is intended for wintering brant geese and black ducks from as far north as Labrador that scores of volunteers have been feeding for the past 10 days. Record freezing temperatures have covered the birds' 200-mile stretch of the Jersey shoreline.

Mrs. Roger Foy's Three Bay Duck Fund has raised about $1,200 in voluntary contributions in the past two weeks and the first of the money went to pay for today's corn. The helicopter unit from Lakehurst Naval Air Station volunteered to provide the air drop.

"The feeding is starting to pay off," said Foy, wife of a retired Philadelphia civil servant and a year-round resident of this resort community. "We're not digging birds out of the ice anymore. They seem to be making an improvement."

State environmental authorities officially discourage aidrop feeds because, as George Howard puts at, the disturbing noise of helicopters and planes "cause the birds to use up energy that they really need to stay alive." But Howard, chief of New Jersey Division of Fish and Game, said the state is depending on people like the Foys to stem the birds' mortality rates.

Foy's effort is only one of many. Volunteers began daily feedings last week and it is estimated that thousands of dollars had already been spent on feed before today's airdrop.

The state has established some 100 feeding stations in the coastal marsh-lands where the brants and black ducks normally winter. State officials estimate about 13,000 brants and up to 50,000 black ducks have been affected by the severe weather. Thousands more are believed to have fled further south.

"Thousands of brants died," said Howard, "and hundreds of black ducks. They don't normally eat corn but Hurricane Belle destroyed the eel grass and by cabbage that they fed on last summer. They apparently turned to algae in the ponds and marshes until it was covered with ice."

Partially frozen and dying birds have sought refuge in suburban communities all along the New Jersey shoreline and last week volunteers were daily digging them out of layers of ice along the beaches and bay. An accurate estimates of stricken birds, officials say, will have to wait for a thaw.

Even then it may not be possible, Howard said, because scavanging seagulls are consuming the dead. "It's altogether a natural phenomenon," he said, "and nature's way is that nothing goes to waste."