BREWER — The female bald eagle that ingested an unknown toxin and fell ill in Bangor three weeks ago emerged from a large dog crate, flapped its wings, and returned to the wild on Tuesday afternoon.

The eagle, dubbed “Bangor Mom” by biologists, flew across a pond at the Penobscot County Conservation Association and landed softly near the top of a tall evergreen tree a couple hundred yards away. It was released by Brad Allen of the Maine Department of Inland Fisheries and Wildlife and Marc Payne of Avian Haven, the rehabilitation facility the eagle was taken to in May.

The eagle was found, disoriented, on a Bangor sidewalk on May 11. Its mate also apparently ill, was electrocuted hours later. Observers said the male lost its grip on a branch and tumbled into a power line.

Brad Allen, bird group leader for the DIF&W, said the department is waiting for necessary permits before the male eagle’s remains are tested in hopes of learning what toxin was ingested. The female eagle did have an elevated level of lead in its blood, but the lead poisoning was not at a high enough level to lead to its behavior, according to Allen and Payne.

But Allen said that anything that eats a poisonous substance and dies, then is subsequently eaten by an eagle, could be to blame.

“These eagles are supposed to be operating above treetop level,” Allen said. “When they get down on the sidewalk, there can be some problems.”

The female bird was fed a solution of activated charcoal to treat its exposure to a toxin and became more alert the day after it arrived in Freedom. It made steady progress after that, Diane Winn, co-owner of Avian Haven said.

“It just seemed to be a matter of time,” Winn said. “She didn’t eat very well for maybe the first week or so, but once she seemed to get her bearings, she made fairly rapid progress from being clumsy and stumbly to flying a little bit, to flying a little bit more, to flying very well.”

Payne said the eagle eventually was moved to a large indoor cage where she could strengthen her flying muscles while flying as many laps around a 160-foot loop as she wanted.

Payne has released plenty of eagles over the years, and said when the top is removed from the crate, many things can happen. He said Tuesday’s release was close to perfect.

“She cleared the trees,” he said with a chuckle, referring to a line of shorter trees that border the pond. “It’s unpredictable, but for the most part we have large enough cages [at Avian Haven] so that we can evaluate her flight.”

Winn said nine eagles are being rehabilitated at Avian Haven, and when “Bangor Mom” was put in the company of other eagles, the bird started eating again.

A day after the adult pair eagles were stricken, biologists and an expert tree climber rescued two eaglets from their nest in a 90-foot pine tree on Kenduskeag Avenue in Bangor.

Those eaglets also are at Avian Haven, but attempts to reunite them with their mother were not successful, Winn said.

“It’s a very unusual situation to have a parent and some babies rescued at the same time,” Winn said Monday. “In the few instances that we’ve had here, or heard happen elsewhere, almost every time, the parent has not had any interaction with the kids.”

Those eaglets are thriving even without their mother and weigh about 4 kilograms (8.8 pounds) apiece, Winn said.

“They’re starting to get their darker nestling feathers and lose their gray baby feathers,” she said.

Winn said it’s too early to determine the gender of the eaglets, but one is significantly larger than the other, leading her to believe that one may be a male and the other a female.

If their rehabilitation goes as planned, Winn said the eaglets could be reintroduced to the wild this fall.

“When we get nest drop-outs, we usually hold them through the summer into the fall, until the family groups disperse,” she said.

Through the summer, Winn said she’d introduce the eaglets to other juvenile eagles as Avian Haven receives more birds, with an end goal of releasing them into a place with ample food in the fall.

Allen said the eagle released on Tuesday should handle her newfound freedom seamlessly, with her sole focus becoming food. Although she was released across the river from her previous Bangor nest, the biologist said the eagle is very familiar with the area surrounding the release site, and likely fished the small pond she flew over to perch in a tree.

The eagle is still fairly young — 6 years old, according to leg bands — and bald eagles can live well into their 20s.

“You’ve taken all of that [parental responsibility] out of the picture. She has no mate, which will probably change pretty soon,” Allen said. “The nesting period is done for her [this year] so all she has to do is survive to nest again in another year.”

Sharon Fiedler, a Bangor wildlife photographer who has taken many photos of the nesting pair of eagles over the past few years, was on hand in Brewer for the release.

“I thought it was awesome. Just awesome,” Fiedler said. “We’re hoping she comes back [to the nest on Kenduskeag Avenue]. That’s what I’m hoping, that she comes back to her nest. Here’s hoping. It’ll be nice to have her home.”