When two swan families decide to fight, a community faces a tough choice.

Some years ago, I felt compelled to get involved in another couple’s domestic dispute. My usual policy about such entanglements is to steer clear of them. This particular situation, however, happened to involve the woman who lived in the apartment across from mine, and I was legitimately concerned for her life. Insofar as the victim’s abusive husband also happened to be my landlord, I soon found myself out of a nice apartment. But that’s another story. The one I happened into recently involves a domestic dispute of a whole other order, and another species entirely.

Two new sets of highly protective swan parents are intent on raising their respective broods in the same lake waters of my neighborhood park. Experts say such territorial disputes are common among wild swans; they go on all the time without our ever being aware of them. This particular swan war, however, happens to be unfolding on the most public of stages, the man-made lakes of Brooklyn’s Prospect Park, and the wake from the battle is now upsetting both humans and swans alike.

The roots of the upheaval trace back nearly a century and a half, to when the renowned landscape architects Fredrick Law Olmsted and Calvert Vaux, who together designed Manhattan’s Central Park, turned their attentions to Brooklyn. In 1873 they completed the 585-acre expanse of rolling meadows, deep wooded ravines, and winding waterways that now constitute Prospect Park, the work both men considered their true visionary masterpiece. Much of Brooklyn’s current urban sprawl had yet to encroach on the park’s borders, making Prospect Park a kind of anticipatory buffer against the coming onslaught of cement: a living pastoral idyll that has drawn in far more than just beleaguered urbanites. Along with squirrels, chipmunks, snakes, fish, and turtles, countless species of birds have come to consider the park their refuge. It’s an oasis-like stopover for the many migratory species traveling along the Atlantic flyway, and a permanent home for everything from red-tailed hawks to mute swans.

“Mute swans” is something of a misnomer considering the notable hissing, grunting, and snorting noises these swans make, especially in the heat of battle. Native to Eurasia, mute swans were first brought to the U.S. around the time Prospect Park was being built. Their distinctive all-white bodies, sinuous necks, and bright orange bills set off by a deep black knob at the base, made them the perfect ornaments for ponds and lakes in urban park ponds. But Olmsted and Vaux’s recreation of wild habitat proved so convincing that the ornamental swans soon began reverting to feral ones. And in the 1980s, when one resident couple successfully bred and raised their own cygnets on Prospect Park Lake, so was born a whole new way of thinking among the park’s caretakers.

All at once in the course of my daily park walks (I’ve lived just up the block from Prospect Park for nearly three decades), I was confronted by fencing that confined me and other park visitors to assigned pathways, and with signs everywhere explaining that the place was “Going Natural!” or “Back to the Wild.” Humans, the very species that Prospect Park was originally intended to attract as an antidote to urban constriction, were now being constricted within the park’s borders, to allow the grounds to recover from years of human trampling and attendant erosion.

The plan struck some people as extreme. But others—especially certain non-humans—benefited. Soon a second mute-swan couple had taken up residence in Prospect Park Lake and everything seemed well in urban paradise. At 60 acres, the lake was plenty big enough to accommodate both pairs; one kept to the north end of the lake and the other to the south. But just last year, both swan couples hatched young cygnets at the same time, and that’s when the trouble started.

The war has been imbalanced from the start. The southern family hatched four cygnets, all male, while the northern family hatched just one. And the southern family has been ferocious in its mission to evict the northern clan. The father is the main culprit, streaking in like a dive bomber, squawking and flapping and repeatedly jumping on the northern parents and their baby, trying his best to drown them. The rest of the southern family also joins the assaults, often leaving their northern counterparts dazed and stranded on the lake’s shores. Park visitors have placed a number of outraged calls to city and state agencies, asking them to intercede. But everyone from park officials to animal experts have steadfastly refused; their rule of thumb in these cases is to stand back and allow the very nature that the park’s caretakers have so courted to now take its course.

“I can understand it’s disturbing,” Eugene Patron, a spokesman for the Prospect Park Alliance, which overseas all park functions and maintenance, told a local newpaper. But trying to intervene will “probably stress the whole situation.”

Still, just as swans are deeply territorial, we humans consider ourselves intrinsically fair. Concerned citizens now gather daily at the Audubon Center in the park boathouse at the northern end of the lake, ready to step in and chase the southern aggressors off. Sometimes they bring cups of food and water to the exiled northern clan to keep them from getting weak and dehydrated. One particularly vigilant couple travels over a half-hour every day from their home in Sunset Park to keep watch over the northern swans. They’ve even named the family’s besieged single male cygnet “Honey Bear” because of the distinctively usrsine utterances he makes. The southern family’s petulant patriarch, meanwhile, is known now simply as “the monster.” One recent weekend, I actually saw the Sunset Park couple and a group of helpers bodily lifting the northern swans from the shores of Prospect Park Lake. They were trying to transport them to a smaller, seemingly safer patch of water in the lake’s main estuary on the far side of a nearby granite footbridge. But when one of the swans broke free from its would-be rescuers arms and headed back to their contested quarters on the lake proper, the attempted transplant was abandoned.

So far I’ve stuck to my policy of non-involvement, even as I empathize with the plight of the northern swans and the actions of their ardent human defenders. Of course, whether nature—even a man-made rendering of it—will yield to such efforts is not at all clear. Giving food “and rooting for swans—that doesn’t work,” Susan Elbin, an Audubon Society ornithologist and mute swan expert explained to one newspaper reporter. “One animal is going to win, and one animal is going to lose.”

Charles Siebert is a contributing writer for The New York Times Magazine and is the author most recently “The Wauchula Woods Accord: Toward a New Understanding of Animals.”