Virginia Republican Sens. John W. Warner and Paul S. Trible Jr. last week asked Senate committees to allocate $3 million in the 1984 federal budget for the protection of bald eagles in the Mason Neck wildlife refuge.

The $3 million would be used to buy the remaining 355 acres of privately owned land inside the refuge, land that otherwise is slated to become a housing subdivision.

That development, conservationists fear, would threaten the eagles' favorite nesting areas in trees about 400 yards from the proposed subdivision. Eagles are shy birds and have been known to abandon nests when disturbed.

A similar $3 million allocation was blocked last year in a congressional conference committee after it had been approved by the House.

Trible's support last week came as a pleasant surprise to conservationists because "he doesn't have the background and is a new senator unfamiliar with the issue," said Elizabeth Hartwell, who has worked to help create the network of federal, state and regional parks established on Mason Neck in the last decade, which now total more than 4,000 acres.

Trible explained his support by saying that "it's critical as well as symbolically important to ensure the future of a bald eagle habitat within sight of the Capitol."

A spokesman for Warner, a strong supporter of buying the last private holdings in the refuge, said, "It's too early to bet, but we're hopeful this may be" the year the funds are approved.

The Reagan administration has included no money for Mason Neck--in fact, little is included for any federal parkland purchases--in its 1984 budget.

The Department of Interior considers Mason Neck among its top three priority land acquisitions, Fish and Wildlife Service officials told Hartwell and other conservationists at a January meeting, although there are no plans to buy the land before 1985.

Hartwell said: "This year, I think we'll have the support of the entire Virginia delegation, and I'm sure Gov. Charles S. Robb will be behind us again. What we need now is more citizen support to help us lobby Congress because, after all, this has been a citizen effort from the beginning."

The Audubon Naturalist Society, which started bald eagle surveys in the Washington region 26 years ago, will sponsor a meeting tomorrow night to create a permanent Mason Neck conservation organization "to concentrate primarily on park problems . . . because there are always threats on Mason Neck," Hartwell said.

The meeting is scheduled for 7:30 at the Mount Vernon government center near Mount Vernon Hospital.

Last year at Mason Neck, not only were bobcats, otters and a golden eagle seen for the first time in many years on the peninsula, wildlife refuge manager Domenick Ciccone said, but 17 bald eagles were spotted at one time wintering beside the Potomac River, more than had been seen since the 1940s.

The nation's lower 48-state bald eagle population, now up to about 5,000, had dropped to less than 1,000 in the early 1970s because of the widespread use of the pesticide DDT, which weakens eggshells.

"This winter has been mild and only 14 bald eagles have been spotted on Mason Neck," Ciccone said. "But we've seen our one nesting pair breaking branches and presumably carrying them off to a nest, and that's a good sign."

Last year, a similar nesting pair had its nest destroyed by high winds. It was the second time in two years that winds had toppled an eagle's nest on the refuge.