SPRINGFIELD, Mass. (AP) _ Wildlife officials on Monday staked out a red oak tree by a reservoir where the first pair of bald eagles to nest in Massachusetts in nearly 80 years is believed to be guarding a clutch of eggs.

''The evidence is still purely circumstantial, but the female refused to leave the nest when approached and the male has been bringing her food,'' said Ellie Horwitz, a spokeswoman for the state Division of Fisheries and Wildlife.

The male is Ross, one of the first pairs of eagles raised and released in the restoration program begun in 1982. His mate is another state-raised bird released in 1985, Ms. Horwitz said.

Over the last seven summers the state has raised and released 42 bald eagles at the Quabbin Reservoir in western Massachusetts.

Two other bald eagle pairs built nests at the reservoir this spring, and there is a possibility that a second pair could also have eggs, Ms. Horwitz said. The third pair are believed to be younger birds practicing housekeeping as Ross and his mate did last spring, she said.

The last active bald eagle nest in Massachusetts was reported in Sandwich, on Cape Cod, in 1910, she said.

At least four other states - New York, Pennsylvania, New Hampshire and New Jersey - also have active nests this spring, state officials said.

''The bald eagle looks to be one of our success stories,'' said Paul Nickerson of the U.S. Fish and Wildlife Service. ''The breeding population is increasing from 5 percent to 10 percent annually.''

He estimated the 48 lower states have about 2,200 breeding pairs of bald eagles, up from 500 to 600 pairs in the 1960s.

Nickerson credited the banning of DDT and other pesticides, which weaken eagle egg shells, and a drop in shooting and trapping.

It may take several years for eagles, which mate for life, and return to the same nests year after year, to learn how to become successful parents, Ms. Horwitz said. Normally they lay from one to three eggs and the young hatch in mid-May, she said.