EDISON – The birds travel thousands of miles, following ancient migratory flyways to land here in the Dismal Swamp and feed or nest: barn swallows, high-flying Canada geese, the red-winged blackbirds of spring.

The debris follows a shorter route. It’s flung from car windows, dumped on the side of the road, or carried by strong winds and local waterways: fast-food wrappers, plastic jugs, empty bottles of household cleaner.

The paths might be different, but the destination is often the same: The Dismal Swamp in Middlesex County, and its picturesque paths like the Songbird Trail, is home to hundreds of birds and a variety of other flora and fauna, but susceptible to the pollution inherent in the middle of the most densely populated state in the nation.

"That’s the battle we have in the Dismal Swamp, period,” said Bob Spiegel, the executive director of the Edison Wetlands Association. “You always find floatables. We’re constantly fighting that battle."

The effort to keep the Songbird Trail clean of trash so that its namesake animals can continue to strike up their song provides a glimpse into the struggle to preserve a last bastion of wild nature in urban Central New Jersey. And while news these days on the environmental front rarely seems to fall short of apocalyptically dire, the Songbird Trail is a notable local exception: a success story in the works.

The work will continue Saturday as the Edison Wetlands Association holds its annual fall festival. From 1 to 5 p.m., the environmental group will offer face-painting, live music, arts and crafts and a cleanup of parts of the Songbird Trail at its Triple C Ranch off Tyler Road.

THE HISTORY

First, a quick primer: The Dismal Swamp is a 1,200-acre conservation area in Central New Jersey, stretching into Metuchen, South Plainfield and Edison. Dubbed the Everglades of northern Middlesex County, the area provides a bulwark against hurricanes, a natural aquifer and a home to a variety of wildlife, including 180 reported bird species, according to one study.

Two years ago, the Edison Wetlands Association, a nonprofit environmental group that runs the 40-acre Triple C Ranch nature preserve in the middle of the swamp, added to its holdings when it opened the Songbird Trail.

It's the nature trail that almost wasn't. The town had once had designs on the pathway. But the plan to extend Nevsky Street to New York Boulevard languished for decades, so instead of a paved street, as was originally envisioned, it’s now a dirt footpath through the woods run by Spiegel’s environmental group. Benches, placards with environmental facts and fliers about recycling line both sides of the path, a quick but scenic jaunt through the woods with a few tributary trails.

In the years since it’s opened, the Songbird Trail has come a long way, according to the people who have worked to clean it. And yet there are always challenges, Spiegel says.

THE CHALLENGES

The Songbird Trail is bound by developments and a public-works yard on all sides. I started taking photographs of birds there this spring (the obligatory birding apologia: Read famous New York City birder Chris Cooper's seven pleasures of birding, or anything by Jonathan Franzen on the subject, both fiction and nonfiction). Mostly out of exasperation, I also started taking pictures of the trash I found while looking for new bird species.

The Triple C Ranch, open since 2001, is pristine. But the Songbird Trail, which leads to the ranch, isn’t.

That's not to say it's overflowing with grime. Far from it. But sometimes you'll see litter and you're almost too confused to be angry about it: Why is there a string of Christmas lights hanging from a tree? What is that hulking piece of rusted metal machinery doing half-submerged in the creek, the same place where you can see mallards swim and great blue herons wade? What is that other hulking piece of rusted metal machinery doing in there, right next to it?

I’m not the only one who’s noticed.

The Chang family lives on Mayercik Court, a sub-development that abuts the Songbird Trail. A few years ago, when the Songbird Trail was just an unkempt patch of land and when illegal dumping was commonplace, Lei Chang took his children out into the woods to pick up trash – the plastic bottles, golf balls and fast-food wrappers that somehow end up in the swamp. It was a matter of pride in their neighborhood.

A deer is seen along the Songbird Trail in Edison.

At first, this cleanup was something of a chore that they did at the behest of their father, said Ann, 25, and Jacob, 17. But they learned to appreciate it.

"It started to become a family thing," Ann said.

Jacob said he recently saw someone dumping a collection of bottles on the side of the road. Jacob approached the guy.

"Are you that lazy?" Jacob wondered.

The man started trying to justify what he was doing. But it turns out there’s no good explanation for throwing trash out of your car, especially into an environmentally sensitive wetland. Jacob took the trash himself and disposed of it properly.

The litter situation in the Dismal Swamp has gotten better, the Changs said, but they still see people dumping trash directly into the woods.

And yet, if one is unlucky enough to worry about this sort of thing, there’s actually even more cause for concern than the people who purposely dump trash in protected conservation land. There are many other ways to indirectly litter in the Dismal Swamp and along the Songbird Trail, even if one isn’t leaving a plastic coffee cup on one of the benches where birders like to sit and wait.

The Triple C Ranch, a 40-acre nature preserve open since 2001, will host the Edison Wetlands Association's fall festival this weekend.

Spiegel, for one, says they’ve pulled countless little pieces of colorful detritus out of the waterways, the result of balloon releases. Bottles from miles away make their way via the Bound Brook and end up in the swamp. Paper can ride wind currents. Stryofoam, too, is a scourge. So even if at first it’s the side of the New Jersey Turnpike, eventually, that fast-food wrapper could end up in a place much more beautiful.

And even the well-intentioned can contribute to the problem. If a recycling bin is overstuffed with bottles, there’s a good chance that they’re not all going to make it to the recycling yard, especially if it’s rainy and windy, Spiegel says.

THE RISKS

So in the end, what’s the harm to wildlife?

In the short-term, the litter can kill birds. In the longer term, the litter can harm the environment, leach poison into the ground, destroy habitats and then, finally, kill birds.

So explains John Cecil, the vice president for conservation at the New Jersey Audubon, an environmental group that focuses on birds.

"We don’t like to see (the trash), and in some ways, it’s the recognition of our impact on the environment," Cecil said. "The idea is, we wouldn’t want someone to throw garbage in our window. We shouldn’t throw garbage in someone else’s home."

Birds might confuse the litter for food. An extreme example of this phenomenon of trash directly harming animals is happening on Midway Island in the Pacific.

Longer-term, Cecil said, we don’t even really have a handle on the effects of plastics breaking down in the environment, potentially leaving behind toxins and ruining habitats. Some birds will be able to cope. Others won’t. If birds aren’t your thing, you can replace them with something else in these examples – turtles, for example, are just as susceptible to confusing a deflated balloon for a nice meal.

"It not only looks bad," Cecil said, "it could absolutely have negative effects on wildlife over time."

THE PROGRESS

At one point, trash in the precursor to the Songbird Trail covered the ground from start to finish. Some people used it as a dumping ground for household and even industrial trash. That’s happening less and less now.

And the littering problem there doesn’t approach the environmental calamities that Spiegel’s group has confronted in the past. The Edison Wetlands Association was founded in the 1990s due to public outcry over toxic Superfund sites. A discarded blunt wrapper is unsightly and harmful, but it's not Agent Orange.

More good news: Generationally, the tide is turning in environmentalists’ favor when it comes to perceptions of littering, Spiegel says. Recently, the Triple C Ranch hosted a group of more than 1,150 second-graders. They were hip to the anti-littering lessons, Speigel said, but some adults could learn a thing or two.

"We have to just get it across to people that there’s been a change in the way people perceive these areas, these wetland areas, these natural areas," Spiegel said. "The public has really started to come back out and enjoy what’s close to home."