Eaglets preparing to leave the nest

About two weeks ago, the juveniles began 'branching' -- hopping up the tree boughs, often with wings flapping

Six eagle eyes peer over the steep hillside overlooking the Monongahela River; six jet black wings test the wind as the Hays eaglets warily consider their first leap from the only home they've known.

Across Pittsburgh and around the world, untold numbers of human eyes watch live computer images from a tree-mounted video camera that has documented every movement the birds have ever made, anticipating imminent fledging -- the first flight from the nest.

In December 2013, the Murrysville-based PixController security camera company and state Game Commission set up the high-resolution and night-vision camera system with an independent power source and live video feed to monitor the nest 24/7. Since then the site has logged more than 2.5 million views. On chat and comment boards, virtual "eagle friends" have marveled at the three eaglets' growth, lauded the 51/2-year-old adults' parenting skills, scoffed at sibling rivalries, bristled at unwanted human incursion and shared fears of potential threats to the nest, including a raccoon attack, hungry hawks and thunderstorms.

"Now, they're very nearly fully developed juveniles," said National Aviary ornithologist Bob Mulvihill. "They're about 10 weeks old -- that's right about when they should be fledging."

Last year, when the same eagle couple nested in the Pittsburgh community of Hays, their single eaglet's fledging was more accidental than instinctual. In early June, about seven weeks after hatching, the nest collapsed, dumping the eaglet onto a smaller tree below, where it clung for about three weeks before awkwardly flapping away.

The first of this year's eggs was laid Feb. 19. The "babies" have grown to the size of small turkeys -- so large the family can barely fit in the 5-foot-diameter nest, especially when one of the adults delivers a freshly caught fish in what is sometimes a fly-by-and-drop operation.

About two weeks ago the eaglets began "branching" -- hopping up the tree boughs, often with wings flapping -- sometimes beyond the camera frame. Mr. Mulvihill said the eaglet trio look healthy enough to fledge at any time. "Their wing and tail feathers may be a shade under flight-ready," he said, "but it's typical for birds of all kinds to leave the nest just before they're ready for flight."

There's been little research on the behaviors of bald eagles in urban settings at the Pittsburgh latitude. They may act differently here than they would in rural environments farther north. Mr. Mulvihill said wildlife cameras -- this PixController project in particular -- are providing a new research tool for ornithologists.

Last year, the adult eagles were expected to fly south in search of open water when the Monongahela River froze over. But the camera showed they stayed in town despite the long, cold winter. While egg and eaglet mortality rates are generally high, the successful laying, hatching and developmental processes were shown in high-resolution detail. Eagle watchers noted the parents' ability to work together, and how the last eaglet to hatch -- smaller and sometimes bullied by its siblings -- learned to make Steelers-style end runs around the others to grab food during feeding scrimmages.

Yet much remains unknown, including the eaglets' genders. Mr. Mulvihill said there's no scientific consensus as to whether they will fledge in the order they hatched, if watching the first to leap will prompt the others to follow, how long they will stay near the nest before dispersing and where they'll go when they fly off to begin their adult lives. "It's unlikely they'll return to the nest once they leave," he said.

Threats to the eagles will remain after they have left the camera frame. Learning to find and gather food without getting hurt is difficult for all predators. A large percentage of juvenile bald eagles die of starvation within a year after fledging.

Despite the new technologies, scientists know little about how the eagles know what they know. Details particular to their species including food gathering, choosing a lifelong mate, nest construction, mating rituals, the laying and care of eggs and defense of the nest seem to occur without observational learning. Scientists ponder what prompts the developmental milestones of animals, including when and how the Hays eaglets will know when the time is right to leap from the precipice of their home some 60 feet above a steep hillside, likely never to return again.

"Instinct is perhaps more complicated than you may think," said ornithologist Kevin McGowan at Cornell University. "It isn't just learning vs. instruction, not just nature vs. nurture. It's nature and nurture, they can learn and incorporate new information, but they do a lot of things just because they're eagles."

Eaglets start flapping before their wings have grown strong enough for flight, yet when fully grown their wings are unusually strong and aerodynamic, permitting them to soar without flapping and dive at extreme speed with great maneuverability.

"How do they know to do that? It's instinct, and we don't know exactly what that is," said Mr. McGowan.

Keep up with the eagle family activities via the live cam.

After fledging, juvenile bald eagles routinely dive toward water to pick up sticks and anything floating -- an instinctive precursor to food gathering.

Nest building is particularly fascinating. "It seems to come from a deep set of genes that predisposes them toward putting things together in a structure -- that eagles generally follow the same structure is ... well, we don't know what it is," said Mr. McGowan. "There's evidence that dinosaurs made nests, so they're doing something that is maybe more ancient than birds themselves."

Two additional bald eagle nesting sites in Allegheny County, in Crescent and Harmar, have produced several eaglets this year -- with no cameras or good vantage points researchers say they won't know the number until those birds fledge.

But at the Hays site, the instinctual traits of another species have become evident. The camera and video feed have attracted thousands of viewers, many of whom watch daily and have bonded with the eagle babies in a clear display of human instinct. On chat boards some call them "our darlings," lobby for more protections and give names to the wild animals.

"If humans weren't instinctually driven to protect cute little things with big eyes we might throw our babies out the window," Mr. McGowan said. " 'Cuteness' is an honest to goodness thing. Our affinity for cuteness, or baby-like appearance, has been a successful evolutionary strategy for humans. Bird brains are configured differently than human brains ... but somewhere in there are instinctive behaviors particular to our species, and that's what you're seeing on the chat boards."

This weekend, a meeting was to be held at a restaurant near the nest site. Darlene Halicki of Bridgeville called the first official gathering of the Friends of Hays Eagles support group.

"What we'd like to do is volunteer to help the Game Commission, National Aviary and Audubon Society with educational programs and assist where we're needed," she said.

Their interest in the birds runs deep. "A lot of us are empty nesters, our children have gone and we're now addicted to these babies. Just like mama and papa eagle have a natural instinct to protect, we watch these babies grow and want to protect."

Ms. Halicki said she doesn't think group members are applying human traits to animals; they're just indulging their own human instincts. "I see it as, humans have soul, heart and instinct," she said. "Since I believe in a higher power, I don't believe animals have soul. But I do believe something is going on with these eagles that has drawn me to them. If something [bad] happened to them, we'd be terribly upset."

John Hayes: 412-263-1991, jhayes@post-gazette.com.

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