From high atop Cadillac Mountain in Acadia National Park, volunteers and scientists are marking a big milestone this year at perhaps one of the best spots to watch migrating hawks, falcons and other raptors in North America.

The annual Hawk Watch program on the mountain peak is marking 20 years of operation at the Maine national park.

Located off the Cadillac North Ridge Trail close to the 1,530-foot summit, the viewing area is free to everyone and open from 9 a.m. to 2 p.m. each day, weather permitting, until Oct. 31.

As the raptors soar over Frenchman Bay, amateur bird watchers or just regular people help spot the birds and specialists identify or confirm the species.

Angi King-Johnston, science associate at the Schoodic Institute at Acadia National Park and count compiler for the program, said Hawk Watch shows the beauty of citizens taking part in a science project.

“It’s the brilliance of Hawk Watch,” she said, standing over Frenchman Bay one day at the end of September. “I could not do my job without all the extra help.”

Hawk Watch recently became a collaborative effort between the park’s interpretive division and the institute’s bird ecology program.

Hawk Watch as citizen science

The Schoodic Institute, a non-profit based at Acadia’s Schoodic Education and Research Center campus in the only part of the park on the mainland, works closely with the park to provide research and learning opportunities about nature and science.

The Hawk Watch program is one example of a special public-private Citizen Science Opportunities initiative spearheaded by Schoodic, allowing people to learn about science while participating in research. Friends of Acadia also helps support Hawk Watch.

During our recent visit, King-Johnston was searching for migrating raptors with Anne Donovan of Boston and Elaine and David Zeitlin of Stonington, Ct., all repeat visitors who spend part of their vacations at Hawk Watch.

The Zeitlins experienced an epiphany after visiting Hawk Watch several years ago. They enjoyed it so much they became avid bird watchers and now attend birding conventions. “It was a life changer,” said Elaine Zeitlin.

During a visit on Sept. 17, 2011, the Zeitlins found themselves in the middle of Hawk Watch history when they helped tally 3,014 Broad-winged Hawks that flew over Frenchman Bay in a single day, or almost all of the 3,200 raptors spotted that morning and afternoon.

Edwin W. Hawkes, a master bird carver from Bar Harbor and an official volunteer at Hawk Watch for about the past 15 years, was also there that record-setting day. “The birds were everywhere,” he said. “That was a fun day.”

The direction of the winds can be a major factor. North or northwest winds are the best since the birds are flying south and gliding in the thermals and drafts.

A southerly wind will likely yield few raptors.

When the winds and weather cooperate, the Acadia location is one of the best for watching migrating birds. People can enjoy spectacular views from Cadillac over the islands in Frenchman Bay and unlike many other such hawk vantage points, they don’t need to crane their neck to the sky. You can look mostly slightly down at the birds as they glide over the ocean and land.

Former Acadia park ranger Tony Linforth described it as “one of the best bird-watching spots in North America.”

Hawk Watch can be a stirring experience.

When we visited one sunny August afternoon several years ago, a sharp-shinned hawk emerged from the bay and zipped directly over our heads, flapping its wings in quick bursts.

Even without binoculars, we helped spot other raptors such as northern harriers and ospreys. A ranger provided a quick lesson on how to use the Porcupines and other islands as landmarks to help identify the locations of the birds.

Migrating hawks, or anything in nature, can also seem indifferent to people.

This year, during two separate visits in late September, we were stymied by south winds.

“There’s a turkey vulture,” Hawkes told us during one of our attempts. “That’s about all we’ve seen today.”

Following the hawks

Since 2008, Donovan of Boston has come up to Acadia to participate in Hawk Watch, staying at least a week in the area. She doesn’t mind if there are few birds on a particular day or she needs to bundle up because of cold winds, as on the day Hawkes recently pointed out the sole turkey vulture.

That year, the start of the 2008-2009 financial crisis, was a time of transition for her. “I didn’t know what to do with myself,” said Donovan. So she came up to Acadia and participated in Hawk Watch, which brought her solace.

It’s been an annual migration for Donovan ever since.

According to King-Johnston, in an e-mail dated Oct. 16, Hawk Watch has counted 2,287 raptors so far this year, led by 675 Sharp-shinned Hawks, 644 Broad-winged Hawks and 404 American Kestrels.

The yearly average at Cadillac for all migrating raptors is 2,950.

The web site HawkCount.org includes annual numbers for all species at Acadia and for similar programs in Maine and North America. This is the first year that all the data from Cadillac’s Hawk Watch has been uploaded to the Hawk Count site, a fitting achievement for the 20th anniversary of the Acadia program.

In her e-mail, King-Johnston said the count at Acadia is below average this year with north and northwest winds providing only a few truly good migrating days.

“Some years are like that,” she said in her e-mail. “That’s why continuous yearly counting is so important.”

Back in 1996, for example, 1,469 raptors were counted, far fewer than 2011’s record of 5,422, or the 3,659 total for 2013, according to the web site that includes the Cadillac program and more than 275 other hawk watch sites in North America.

“Although the general trend has been increasing numbers throughout the last 20 years, counts like Cadillac Mountain can help to confirm healthy populations of raptor populations,” King-Johnston said in her e-mail. “Or, if unfortunately necessary, can show a declining population that needs more research and perhaps more observation.”

King-Johnston said it was encouraging, for instance, to help document the recovery of bald eagles. According to the web site, 53 migrating bald eagles were counted at the Acadia site in 2013 and only 13 in 2004.

Whether the numbers are up or down, the migrating raptors of Acadia, on any given day, can offer people an amazing show – and even change lives.