Will A Few Good Terns Attract Others?
Climate change, sea level rise and the inevitable erosion have washed away much of the habitat of once ubiquitous shorebirds in Maryland’s coastal bays and led to a sharp drop in their population.
Now, a coalition of environmental groups and a state agency are banking on a raft made to look like an island to restore what one scientist calls “avian icons of a summer beach.”
Dave Brinker, who monitors bird populations for Maryland’s Department of Natural Resources, says the “raft concept that’s been used other places.”
They built the raft, “covered it with crushed clamshells to recreate a barren habitat for common terns to nest on. And they found it,” he says.
On a recent morning this week, Brinker and a crew from the Maryland Coastal Bays Program and the National Park Service headed out to the raft as a waning gibbous moon hung high in the western sky and the red ball of the sun cut through the haze over the treetops of Assateague Island.
Brinker says the barren, sandy islands in Maryland’s Coastal Bays once were home to nearly 1000 breeding pairs of common terns.
One of them, Skimmer Island, had the largest common tern colony ever recorded in the coastal bays—525 pairs in 1995.
“So, fast forward to 2021 here, and Skimmer Island’s no longer breeding habitat,” he said. “And there's no other good, sand habitat that's very large. And we needed to start replacing the available habitat to keep common terns breeding in Worcester County.”
Roman Jesien, the science coordinator for the Coastal Bays Program, says they found local craftsmen who built the raft in four sections, 16 feet by eight feet each, in their workshop.
“They hauled it over to the boat ramp at South Point, put it together and then hauled it out here on boats,” he said.
David Curson, of the Audubon Society Mid-Atlantic, the other environmental group involved in the effort, says the raft is an interim measure in a larger strategy to rebuild nesting islands in the coastal bays.
“What we really need as well as deploying these nesting rafts is to rebuild natural nesting islands in the coastal bays for these birds,” he said.
The Corps of Engineers already dredges sand from the Ocean City Inlet and offshore to replenish the beaches, he argues. Why not use some of it to restore bird habitat?
“It would take only about 2% of the sand to rebuild one of these birds' main nesting colonies at Skimmer Island. I think that would be a small investment for a big return of stopping these birds from being wiped out in Maryland.”
But for now, it’s the raft, covered with crushed clam shells, dotted with decoy terns and housing a recorder that plays bird calls to attract them. It’s anchored at a spot in Assateague Bay free from predators and away from boats.
Jesien says they had several alternatives that met their criteria and chose this one south of South Point. It’s said to be an “undisclosed location,” but it’s hard to hide something in the middle of Assateague Bay.
Jesien says they were just trying not to call attention to it.
“You can imagine, you know, people want to come out here and jet ski and whatnot just to take a look at it so we’re just kind of shy about identifying where exactly it is,” he explained.
Four orange balls float about 20 yards off the corners of the raft, and just to be sure, there are signs on the corners warning, “AREA CLOSED April 1 to September 15. Wildlife Nesting Area.”
As Brinker eases the bow of his boat against the center of the north side of the raft, the terns erupt in squawks and cries of alarm. He ties off with the help of Tammy Pearl and Abbie Shaw of the National Park Service, part of the crew for this adventure, and steps cautiously onto the raft.
As the terns continue squawking, Brinker works his way around the narrow walkways with his charts, counting nests, eggs, and chicks.
“Because the concept of artificial habitat via raft is sort of new to us, we want to monitor the reproductive success real well, and compare it to what we know from natural sights,” he explains. “So we're keeping track of all the nest contents, all the chicks that are hatched.”
As Brinker finishes his initial count, Pearl slips onto the raft with a small cage, a stick to prop it up and a dummy egg.
Brinker says they use the dummy egg to attract a tern and put the real eggs in an incubator to keep them out of harm’s way. It’s much safer trapping over dummy eggs than live eggs, he explains.
Then they stand off several yards and watch and wait until a tern trips the trap, then head back to the raft.
Pearl and Shaw carefully pull the tern from the trap and slide her into a paper bag then head to a pontoon boat anchored nearby where Jesien and other Coastal Bays scientists await.
While Pearl and Shaw head back to the raft to trap more birds, Brinker stays aboard the pontoon boat to weigh and measure each bird.
He relays the measurements to Kat Phillips, a program coordinator for Coastal Bays, who is standing by with a chart.
She records “wing length, beak length, head length, their weight, and then also just recording the band numbers so they can keep track of which bird has which band numbers associated with it,” she says.
Brinker says the banding will help them keep track of the birds over the years. The first time a bird breeds, he explains, it makes a habitat selection. And if it’s successful it may return to the same habitat the next year.
He says they’re banding the adult birds “so that when we put the raft out next year, and we see birds come back, we can figure out if the same birds are coming back to the raft that used it this year.”
Ideally, Brinker said, the raft should be out in mid-April to catch the first wave of terns as they return, but this one didn’t get out until May. And that had Brinker and the other scientists worried.
“We had nothing on there and we were getting a little worried that the birds weren't going to breed on it,” he said.
He says one wave of birds gets established by Memorial Day, but that one was washed out by an unusually high tide. Since then, however, a second wave has come in.
That could be some of the birds that were washed out over Memorial Day, he says. “Or young birds breeding for the first time that come in and look for habitat.”
It was the second wave that found the raft and has established the 23 nests that are there now.
“For the situation we're in right now I consider this a huge success,” Brinker said.
The raft will stay out until the last chicks have matured enough to fly away, then be hauled off for storage on a nearby property and set out again next spring. Until the chicks are gone, Brinker and the crews from the other agencies will be back each week to check on the progress.