Raptor expert Norman Smith has been working with peregrine falcons for over three decades. But the day each spring when he helps tag falcon chicks atop Boston’s Custom House Tower never gets old.
That day was Thursday.
Smith and his colleagues tagged three chicks — a male and two females — who are a little over 3 weeks old. It’s the only time the birds are handled by humans.
“When you see them after 35 years, it’s just as exciting as the first day you saw them,’’ said Smith, director of Mass Audubon’s Blue Hills Trailside Museum.
Since falcons began nesting in the tower in 1987, crowds have gathered for a chance to see the rare birds.
Thursday’s festivities came with some added drama.
Engineers working on the facade outside the landmark 496-foot-tall building found themselves in a precarious situation when they trespassed into territory that a group of adult falcons saw as their own.
The raptors began dive-bombing the workers in an attempt to protect the young, who had begun squawking in their nest, Smith said.
“Peregrines can be very aggressive when they defend their territory,’’ Smith said, adding that the birds have been recorded flying at speeds up to 242 miles per hour, making them likely the fastest animals in the world.
Wildlife officials placed the babies’ mother in a box to try to stop the attacks, he said, but other birds showed up from around the city to defend the nest. Eventually, the engineers decided to suspend their work for the day.
None of the workers were injured, Smith said — but they were a little spooked.
Banding the baby falcons allows researchers to track their migration patterns and life spans.
Mass Audubon fastens two tags on each chick — one per leg. Smith said the US Fish and Wildlife Service bands one leg with an individual number, “like a Social Security number for birds.’’ On the other, officials place a colored tag with an alphanumeric code, which observers should be able to see from a distance.
“If someone sees [a peregrine falcon], they can identify that individual bird and find out where it came from, how old it is, and where it might have migrated,’’ Smith said. “Because these birds are endangered, it’s important to track and monitor them.’’
Despite their endangered status, he said, about 40 mating pairs of adults call Massachusetts home — more than ever before.
“Ultimately, whatever affects these birds long term is going to affect us,’’ Smith said. “We’re at the top of the food chain, too. By monitoring these birds, they’re an indicator species of what’s going on in the environment.’’
Laney Ruckstuhl can be reached at laney.ruckstuhl.com. Follow her on Twitter @laneyruckstuhl.
