A pair of adult bald eagles has staked claim to a wooded hill overlooking Lake Michigan, preparing to make history this spring.

After finishing a broad nest of large branches in a white pine in early March, they’ve been taking turns sitting on the nest for at least three weeks, indicating to observers that they likely are caring for one or more eggs.

Should the eagles hatch even one youngster, “it would be the first successful nesting of eagles in more than 100 years” in the Milwaukee metropolitan area, said Owen Boyle, a regional ecologist with the state Department of Natural Resources.

The incubation period for eagles is just 35 days, so Boyle and the raptors’ neighbors might know the outcome within two weeks.

“We’re asking people to stay at least 100 yards away from the eagles’ nest,” Boyle said. “Eagles are particularly susceptible to disturbance at this time of year when they’re incubating. No one should approach the nesting tree.”

Harassing eagles is a federal crime. Even if this raptor ultimately is removed from the federal list of threatened and endangered species, the federal Bald and Golden Eagle Protection Act prohibits disturbance of eagles.

Repeated intrusions might prompt the adults to abandon the nest even if eggs have not hatched, Boyle said.

The nesting tree, an old white pine whose top has been bent into the shape of a question mark, is on privately owned property a few miles north of the Milwaukee County line.

Don Edwards, a resident of N. Sheridan Drive, has watched the pair much of the winter as they fished in the open water of the lake.

Now that one of them is always on the nest, Edwards has seen the other taking fish to its partner.

The Ozaukee Washington Land Trust is negotiating purchase of 23 acres of shoreline north of Edwards’ home that includes the nesting tree, said Shawn Graff, executive director of the organization.

Cost of acquiring the property from a developer is $3.5 million, and Graff expects federal and state grants to help pay for all but $1 million of the price.

This likely is the same pair of eagles that built a nest along the Milwaukee River in Mequon last April, though it was too late by that time to lay eggs, Boyle said. That was the first eagle nest to be built in the Milwaukee area in at least a century, Boyle said.

No one is using the riverside nest this year, but other eagles have checked it out, said Anton Usowski, a member of the Mequon Park Board who lives near the city preserve on the river where that nesting tree is located.

Ice went out of the river upstream of the Thiensville dam on March 15, and two days later Usowski observed a pair of mature eagles standing on the edge of the nest there.

The river visitors must have been a different pair of eagles than the lake shoreline nesters, according to Edwards.

The DNR plans an aerial survey of Ozaukee County in April that will count eagle nests and help determine whether more than one pair of the large raptors have moved into the metropolitan area, Boyle said.

If eaglets have hatched in the Mequon lakeshore nest, the aerial observer will spot them next month.

“This is a historic event for southeastern Wisconsin,” he said.