Game Commission officials are excited.

Back in the 1930s, Presque Isle State Park had 100 breeding pairs of terns at Gull Point on its east end before the population collapsed. Recent years have seen terns visit and attempt to nest, but it didn’t work out for the blue-jay sized shorebirds, which have a grayish body, black head, a red beak and legs, and a deeply forked tail.

But the last successful tern nest in Pennsylvania was in the 1960s.

With this pair, bird enthusiasts hope it’s the start of a revived tern colony for the relatively long-lived birds, which can survive to a quarter-century.

With some luck and outside advice, the price tag of reshoring the tern here was also shockingly low: $350 on equipment, not counting personnel time. The Game Commission built a wooden exclosure around the tern nest to protect it from predators.

“It’s probably the cheapest success of a species ever,” PGC Endangered Bird Specialist Patti Barber said. “Most of it, maybe all of it, we’ll be able to use again next year.”

Keeping a pair matters because terns are social and find safety in numbers. When one succeeds, others follow. Their behavior also changes depending on whether they’re alone or in a colony. Alone, they flee from a threat. Among friends, they chase off predators.

“If you ever walk through a tern colony, you end up covered in guano and vomit because they really want to take you out,” Barber said.

Breeding season starts in the late spring, with terns nesting in May “and very quickly setting up their little tiny territories, where a tern sits and how far they can reach and poke their neighbors,” Barber said. “They’re really attracted to each other, but they don’t want to be that close — ‘don’t touch me,’ like kids in the backseat.” Tern chicks then fledge in mid-August.

Great Gull Island, off Long Island Sound in New York, hosts about 20,000 terns that will hit people who walk in the colony.

“They know, once we pass them and walk out there, then we’re done harassing them. They will literally land a foot behind you back on their nest and go back to doing normal tern things,” Barber said. “They’re probably thinking, I scared the big, bad predator away. But when you only have a single bird or a couple pairs, they’re much less likely to do that.”

But that behavior, and significant numbers of breeding pairs, is still years away in Pennsylvania. Terns have attempted to nest on Presque Isle regularly since 2012 (one year had as many as eight pairs on the beach), but all of their 21 nests failed.

Human activity or predators — gulls, crows, and other birds, along with mammals like raccoons, possums, weasels, and cats, don’t ignore a ground-level snack — have undermined any success.

This time around, after the nesting pair’s first nest with three eggs failed, the Game Commission decided to try and protect the second, two-egg nest with an eight-foot wooden exclosure based off a design used by Canadians in Ontario at a tern nesting ground.

“These were the only birds in Pennsylvania. This is our only shot, really, at bringing them back as breeding birds,” Barber said. “We decided we’d try it, even though it seems a little nutty. Since it worked, I think the Game Commission will do the same thing next year. But instead of waiting and letting their first nest fail, we’ll put the box around the first nest — and hopefully they’ll be successful. There’s no guarantee they’ll be successful just because we put the exclosure up, but we stacked the deck.”

The return of the tern has shown how luck, chance, and the buy-in of the public matters.

Officials removed invasive vegetation from Presque Isle and sand naturally piles up on it, creating more beach, which made tern-friendly habitat. The exclosure was much smaller than the ones used in Canada and hadn’t been tried before, but it still worked. And people — from conservationists working to bring back shorebirds to members of the general public who decided not to let their dogs run free on a closed beach — aided the recovery.

Even the birds helped out, despite years of failure on Presque Isle.

“We had this nice, stubborn pair that kept coming back for us,” Barber said. “But they weren’t getting ahead.”

That pair bodes well because success is cumulative. Terns tend to use the same breeding grounds every year, which attracts other breeding pairs, and those offspring follow their parents. A nesting pair that succeeds creates a tradition by attracting other mature pairs while providing a place for their progeny.

Terns also signal the renewal of nature in Pennsylvania.

“All of our birds are being affected by decreased habitat quality and amount of habitat available— all along the eastern seaboard and the Great Lakes, the land has been developed, a lot of those pristine beaches aren’t there anymore,” Barber said. “(Terns) are a great indication of overall habitat health: beach, land, and water because they forage exclusively in the water.”

Other birds, like the spotted sandpiper, killdeer, and piping plover benefit from habitat improvement on Presque Isle, she noted, along with birds migrating through the area in the fall — of which numbers have grown dramatically.

“We hope we’re starting to create a good cycle where, in the past, we were cycling down. We hope we broke that cycle now and we can do a little bit better,” Barber said.

Formal discussion and planning hasn’t happened yet, but the PGC isn’t assuming the future is assured.

“It seems like whenever you count on something, especially with wildlife, that’s when something happens to it. Do not jinx these birds,” Barber said. “Our marketing folks were getting ready to do something for National Beach Day, they were gonna talk about plovers in (Gull) Point and the terns, asking me how many young they raised. I’m like nope, can’t talk to you about that, have to wait until they fly.”

The PGC emphasized that this achievement is the result of partnerships: with the Erie Bird Observatory, the Western Pennsylvania Conservancy, the Department of Conservation and Natural Resources — and Pennsylvania residents of all stripes.

“It’s what individuals do, the decisions they make,” Barber said. “The people that make sure they cut their six-pack holders so none of the critters can get stuck in the holes — and I say it that way because we’ve found terns (elsewhere) that died because of plastic trash … All those individual decisions that we make actually make a difference.”