MAURICE RIVER TOWNSHIP — They gathered as the sun fell, a dozen pilgrims walking to the top of a nondescript concrete bridge overlooking western Cumberland County.
The visitors carried binoculars and talked quietly among themselves as the sky softened to a pink hue.
Each August on the Maurice River, little birds called purple martins gather by the thousands — the tens of thousands — in a phenomenon that has become as predictable as the tides.
The spectacle — and this year, experts said it is truly spectacular — attracts such wide-scale interest, that the nonprofit group Citizens United to Protect the Maurice River created an annual festival around it.
“It is really impressive,” said Pete Dunne, a Maurice River Township resident and director of New Jersey Audubon’s Cape May Bird Observatory. “You have an extraordinary, world-class, natural-history event in your backyard. It begs the question: Why isn’t everybody there to see it?”
The bridge on Route 670 over the Maurice River overlooks a pastoral scene common to the Delaware Bay. To the east, farmland and marsh dominate the landscape broken by patches of oaks, maples and red cedars. To the west, acres of boundless marsh grass called phragmites stretches to a distant tree line several miles away.
It seems an odd place for an annual gathering of 200,000 birds, which makes the phenomenon all the more of a mystery.
Dunne said the cover provided by the sea of marsh reeds is the reason the birds flock here each summer, spreading out in a 50-mile radius to feed each day before returning in one swirling superflock to roost in the reeds at sunset each night.
More than 100 people gathered around the bridge Saturday to view the natural show, said Jane Morton Galetto, a Millville resident and director of Citizens United. Another 60 people took a boat ride sponsored by the group.
“A number of people described it like a tornado. The birds got up and swirled around. They really darkened the sky,” she said.
Purple martins are dependent on people to provide artificial nest boxes and gourds in their backyards, she said. People are taking good care of New Jersey’s resident population of swallows, she said.
“For martins, it’s all about being a good landlord,” she said.
The promise of a spectacle attracted a dozen birders on a recent weeknight, including Maurice River Township residents Walt Birbeck and Eileen Wiggins.
They make a point each summer to stop by the bridge when they can to appreciate the gathering, which includes tree swallows, barn swallows and kingbirds.
“It’s a good year,” Birbeck said. “The first year we came, we thought we missed it.”
Like others, they parked at the boat ramp and walked up the narrow sidewalk to the top of the bridge over the Maurice River, where they had an unobstructed view of the river and marshes.
With the sun an hour from setting, birds were easy to find but not in numbers that anyone might notice as they flitted over the bridge in search of insects.
Purple martins tweeted nonmusically overhead. They flapped their wings in the headwind as if sprinting in a race before soaring as long as they could and resuming their feverish pace.
As the sun dipped lower, more birds began to arrive over the marsh in a disorganized avian mass that reached high into the air like the beginnings of a tornado column. At dusk, with the sun a memory, the birds reached their peak in numbers, a dizzying swarm of feathers that filled the air.
Wiggins said it is especially amazing when the superflock draws near over the bridge. Sometimes, though not on this night, the birds flock together in a single amorphous cloud like a giant flying organism. It is on these occasions that the phenomenon can most be appreciated, Wiggins said.
“You know how in Star Wars when you have that black space and all the stars fly by? It’s like that,” she said.
Binoculars are essential to appreciate the spectacle, which can be distant and hard to see in the low light. But the numbers are startling.
“It’s really hard to capture or photograph the sheer scope of it,” Wiggins said. “It just spreads all across the sky.”
Dunne said in most years, the first flock will head south to Brazil in early August before a new group of southbound migrants takes their place. So, spectators can expect to witness this nightly display through September.
“There are usually two buildups,” he said. “The birds in the roost now could go at any time. There’s a now-you-see-it, now-you-don’t quality about it. There will be a second buildup until the first few days of September.”
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