The bald eagle appeared calm, sitting motionless in the wildlife rehabilitator’s arms. But a fierceness emanated from the bird’s pale yellow eyes. With expert movements, Marc Payne cradled the wild bird, trapping its massive wings against his body while he keeping a firm hold of its powerful feet. Each toe was tipped with a long, curved talon, designed for snatching fish and ducks from the water.

The eagle was one of nearly 2,500 birds that Avian Haven accepted for rehabilitation in 2016 — which is an increase of 1,000 birds helped compared to five years ago. Located in the small rural town of Freedom, the bird rehab center continues to grow each year, and the founders of the center expect it will only continue to expand.

“We anticipated growth, but not this much,” said Diane Winn, who co-founded Avian Haven with Payne in 1999. “I believe we are now the largest wild bird rehab facility in northern New England.”

Avian Haven accepts injured, orphaned and sick birds of any species, but their most well-known “patients” are bald eagles and loons, both of which are iconic birds in Maine.

The female adult eagle Payne was handling had come to the center with lead poisoning in early November and had been at the center ever since, slowly recovering. It was time to test the eagle’s blood. If the lead levels were low enough, the bird could be released back into the wild.

“We’re hoping she’s good to go,” said Kim Chavez, one of the four full time employees at Avian Haven and a Unity College graduate.

Wearing elkskin gloves lined with Kevlar, Chavez and Payne had used nets to retrieve the eagle from its enclosure in one of Avian Haven’s many outbuildings, which were designed and constructed specifically to house birds by Terry Heitz, a carpenter and cabinetmaker by trade who has been working for Avian Haven since the beginning. Walking slowly along a snowy path, Payne carried the eagle to the building that serves at the hub of Avian Haven, into a lab room filled with the equipment they need to care for a wide variety of birds, from baby rock pigeons to great blue herons.

The room had everything from an X-ray machine to a washing machine.

When Avian Haven was established in 1999, it consisted of two buildings and the lab didn’t exist. In that first year, the nonprofit organization accepted about 300 birds for rehabilitation. Winn and Payne realized they needed to expand, and since then, they’ve added at least one building to the complex every year.

“It has a mind of its own,” Winn said about the growing complex, smiling.

As the Avian Haven compound has expanded, so has the nonprofit’s volunteer base, as well as its fulltime and seasonal staff. The center has also developed a crucial network of volunteers that transport birds from all over the state to the facility for treatment. Winn attributes much of Avian Haven’s growth to that volunteer base, as well as the increasing use of social media by the public.

“If people who find an injured bird search for help online, they will quickly find our website and our Facebook page,” Winn said.

Avian Haven staff and volunteers use Facebook and the center’s website to share their experiences with the public through photographs and videos of the birds being treated. This is an important educational tool for Avian Haven because their birds are never put on display. In fact, the center’s staff and volunteers works hard to limit their own interactions with the birds.

“We want to minimize their familiarity with people so they can make a good transition back into the wild,” Diane said, pointing out that it’s also a requirement of their state and federal permits that they not put birds on display to the public.

“Many rehab centers also have education birds held under a different kind of permit,” Diane explained. “We do not have any birds that are taken out for programs or put on display, so in terms of members of the public seeing what we do here, we’re really limited.”

However, Avian Haven does have a special group of permanent avian residents that act as foster parents to young (typically orphaned) birds that the center inevitably receives each spring. These “foster birds” are non-releasable, meaning they have some injury, sickness or disposition that can’t be fixed and makes it so they wouldn’t survive if released back into the wild.

“Their job is to foster parent young birds so that these youngsters grow up knowing what species they are rather than improperly imprinting to humans, which we don’t want to have happen,” Winn said. “Plus, to be honest, it takes a little bit off our work load. Often these foster parents will feed the youngsters so we don’t have to.”

The current foster birds at Avian Haven are two barred owls, two common ravens, an American crow, an American kestrel, a great horned owl, a bald eagle and a mallard.

“I don’t speak raven, but they do,” said Payne as he stood in the doorway of the massive raven and crow house, motioning to the two ravens — both foster birds — perched on the rafters overhead. “The building is built to give them a good view. Ravens like to be up high.”

Twisting their heads from side to side, the two black birds inspected Payne and volunteer Sue Stone, who was busy feeding them and cleaning the sand floor of the enclosure. Every once in awhile, the two foster birds would make low gurgling noises to each other.

Scientists have placed raven vocalizations into as many as 33 different categories based on sound and context, according to the Cornell Lab of Ornithology. It’s important that the young ravens that Avian Haven receives learn to speak this language before being released back into the wild.

Both of the foster ravens have wing injuries that have rendered them flightless, so they wouldn’t survive if released back into the wild. To reach the top of the enclosure, the ravens climb, hopping among pegs that protrude from the wall. From their perch, the two ravens could see through the mesh window to the Avian Haven compound and the surrounding forest.

Winter is slow season for the rehab center, but there were still plenty of birds being housed in the outbuildings. In the pool hall, a red-throated loon swam in the largest heated pool, while an eider duck and a black scoter swam in two smaller pools. Another building housed a golden eagle. But the center’s most plentiful species undergoing treatment at the moment is barred owls.

“We have had an unprecedented influx of car-hit barred owls in the last quarter of the year,” Winn said.

Since Oct. 1, the number of barred owls admitted to Avian Haven has been at least double the number in the same time frame of 2015 and 2014. Many have wing and eye injuries.

“We don’t have a good explanation,” Winn said. “Owls do start hunting roadsides when there is significant snow cover, but we had mild temperatures and no snow at all for much of that three-month period.”

Fortunately, barred owls tend to get along in the enclosures. In a strange location, they aren’t compelled to protect territory or breed; they just co-exist, and hopefully, heal.

To date, Avian Haven has rehabilitated and released approximately 7,000 wild birds.

The facility is financed through donations and grants. Volunteers help keep overhead low. The names of major donors grace the many bird enclosures on the property.

“Some people make donations in memory of a deceased loved one or gift donations that honor a friend or relative,” Winn said. “Others include us in their estate planning, providing a legacy that will help sustain us long term.”

“So far, we’ve been able to stay on top of things,” Winn said, “but our operating expenses have increased along with our caseload.”

The public can help indirectly by keeping birds safe, Winn pointed out, suggesting that people keep their cats indoors, reducing the likelihood of birds striking windows with products such as bird tape and switching to using non-lead ammunition and fishing tackle.

“We are seeing increasing instances of lead poisoning in bald eagles,” said Winn, who reported that in 2016, excluding nestlings and premature fledglings, about 75 percent of the eagles admitted to Avian Haven had elevated blood lead levels. While in years prior, the center hadn’t seen anything higher than 50 percent of their eagles with lead poisoning.

“Eagles ingest lead when they scavenge gut piles or carcasses that have been shot with lead ammunition,” Winn explained. “Some of these birds have massive exposures that are rapidly fatal. Others have sub-lethal exposures that produced impaired coordination that, in turn, contributed to an injury that may or may not be fixable.”

On Jan. 4, with the help of Avian Haven volunteer Sue Stone, Payne stretched the female eagle’s right wing out to the side, and Chavez knelt in front of the bird, moving its dark feathers aside to reveal its pale skin. She then carefully drew a vile of blood from a vein in the wing as Payne blocked the bird’s view with his arm.

Payne then weighed the eagle in a basket and carried it back to its enclosure, Stone opening doors for him along the way.

In the lab, Chavez tested the blood using a small machine invented to test lead in the blood of inner city children. The test took only a few minutes, and Chavez smiled at the reading. The lead in the eagle’s blood was down to a safe level. It was time to set her free.

Aislinn Sarnacki is a Maine outdoors writer and the author of three Maine hiking guidebooks including “Family Friendly Hikes in Maine.” Find her on Twitter and Facebook @1minhikegirl. You can also...