K/Z, a male bald eagle, swoops down from the heavens, his razor-sharp talons dip just below the water’s surface, and seizes a fish. Then, without stopping, he zooms off to the nest a quarter mile away. What was once a white sucker (who’s the sucker now?) is soon to be dinner for three baby eaglets.

The comeback of the bald eagle in Massachusetts since DDT decimated them in the mid-20th century has been impressive. In 1967 they were listed as endangered. Now they are thriving. By 2023 there were 90 pairs of bald eagles identified in the state, according to MassWildlife.

This scene along the Mystic River Watershed is witnessed by a loyal following of birders with spotting scopes and wildlife photographers toting long telephoto lenses.

Several birders commute between there and Woburn, where there are four baby peregrine falcons nesting halfway up a quarry. Peregrine falcons were completely gone from the entire Eastern United States in 1966; by 2023 there were at least 44 nesting pairs in Massachusetts.

Don’t think of the bird photographers as paparazzi, either. Former Globe wildlife photographer Mark Wilson rescued one of the peregrine babies, whose attempt to fly left him stranded on the roof of a parked SUV in a mall parking lot. He gently returned it to safety.

Back at the Medford-Arlington line, K/Z is admired as a rock star. His comings and goings are met with “ooohs” and “ahhhs.”

Life has not been easy for this majestic bird. And we know this because Mass Wildlife banded him as a chick nine years ago at what is known as Webster Lake.

In 2019, he started hanging out with M/K, an outgoing bald eagle who became a cause célèbre in Arlington. Their names are taken from lettering on the orange bands that MassWildlife has used for three decades to track bald eagles. He and M/K have been the subject of two children’s books and were well known by birders, photographers, and local residents who begged journalists not to publish his exact nesting location.

After trying unsuccessfully for a year, they hatched two chicks.

Sadly, one of them died of rodenticide poisoning and the other was struck and killed by a car in Delaware, according to Paul Roberts, a wildlife expert who has been observing K/Z for more than five years and hawks for a half century.

The pair had at least two different nests during their time together and hatched several broods of chicks, according to MassWildlife.

But K/Z started to be challenged by at least six different adult males.

Roberts called it an “avian soap opera.”

One of them, Z/74, who was dubbed “New York” because he was banded in the western part of the state, was extremely aggressive.

“And so, there were extensive chases. And finally, one of the gripping scenes with the attacker swooping down on K/Z, and they rolled over, locked talons, and tumbled out of sight.”

Only New York returned to the nest.

“KZ was assumed dead by many people, but not me,” says Roberts.

Meanwhile, New York was not a fan favorite.

He didn’t share food, he wouldn’t improve the nest, and he was driven by raging hormones during mating season.

“M/K refused to mate with Z/74, who tried repeatedly,” says Roberts. “He had no class.”

A month later, KZ triumphantly returned and reclaimed his kingdom. In a story worthy of a “Sopranos” episode, the New York eagle was soon found dead off a road in Winchester. Fuhgetabout an investigation.

“His body was put on ice, but no tests were ever done to determine cause of death,” says Roberts.

Meanwhile M/K, the queen of the Mystic Lakes and larger than K/Z (by nature females are bigger) was regaled by all that crossed her path. But tragedy struck on Feb. 23, 2023, when M/K was found ill at Mount Pleasant Cemetery in Arlington, showing symptoms of rodenticide poisoning. She died a slow, horrible death coughing up blood, despite the best efforts of the New England Wildlife Centers. Second-generation anticoagulant rodenticides (SGARs) — which prevent blood from clotting — were found in her blood.

Her death prompted an Arlington vigil, an outpouring of love, and a call to reduce rodenticides. It’s sad that eagles, the best rat killers, are killed by ingesting poisons from eating contaminated rodents.

Since 2021, Tufts Wildlife Clinic alone has diagnosed four bald eagles as having died due to anticoagulant rodenticide toxicosis.

Experts say it’s not just raptors that are getting poisoned. It’s owls and coyotes, raccoons, foxes, bobcats, and companion animals. A bill to require pest-control companies to file digital reports documenting that they are using second generation anticoagulants died in the state Legislature last year.

The federal government banned the retail sale of SGARs in 2015, but they are legally used by licensed pest-control professionals in Massachusetts, according to Mass Audubon. These powerful poisons, placed in the now-familiar black boxes outside homes and businesses, are ingested by rodents, which then become easy prey for other creatures. Striking a balance between the need to reduce rat populations and protect wildlife has been difficult.

Save Arlington Wildlife is urging residents to remove their bird feeders through mid-November. They cite studies that say rat burrows are significantly more likely to be found near properties that have bird feeders.

Sam Anderson, Mass Audubon’s director of legislative and government affairs, says eliminating food sources, closing trash cans, and using rat traps instead of poisons can help reduce the problem.

“The black box should only be used in incredibly limited circumstances for a short period of time to address real sanitation and safety issues, and never outside.”

Back at the nest, there was no period of mourning. K/Z had a new mate in his nest the same day, according to multiple sources.

Roberts dubbed her Fae, short for “female adult eagle”, because she has no band number.

She is shyer than M/K was and avoids the limelight. “He is more attuned to people than Fae is,” says Roberts. “He’s a good father.”

These days, K/Z is constantly being harassed by the tiny, territorial eastern kingbirds who make kamikaze dives on him as he flies. They know his weak spot, above and behind his neck. Once the fearless kingbird was photographed flying away with some of K/Z’s feathers. Herring gulls also sometimes try to steal away his catch.

But K/Z’s avoidance dance is breathtaking. He swirls and he whirls and he crosses the lake and touches down softly in the nest with meal intact. To witness the national symbol overcoming adversity and soaring skyward is a heart-thumping thrill.

Stan Grossfeld can be reached at stanley.grossfeld@globe.com.