Deploying decoys to save shorebirds

A “real” tern sits near a decoy. SCCF / COURTESY PHOTO

Shortly after Julie Weaver and John Niesel moved to Sanibel Island from Colorado in 2021, they decided to take a walk on the beach. They spotted what looked like a group of shorebirds sitting on the sand.

They also noticed something strange. “They’re not moving,” Niesel said.

The married couple had encountered a clever ruse devised by the Sanibel-Captiva Conservation Foundation (SCCF) to lure least terns, the smallest terns in the world, to safer, more ideal nesting grounds: Decoys. Little wooden replicas were placed in the sand to show the least terns, listed as threatened by the state, that this was a good place to set up residence, lay their eggs and raise their young.

The SCCF’s April newsletter, “Paving the Way for Least Tern Nesting,” explains why decoys are deployed.

“Least terns are a social species, often spending time together during migration and during the nesting season,” said Aaron White, shorebird technician for the Sanibel-Captiva Conservation Foundation (SCCF). The terns recognize that “birds” are already in a suitable area and they are drawn to nest there, he said. “This is a method known as social attraction.”

Decoy terns sit on the sand to attract “real” birds to preferred nesting areas. SCCF / COURTESY PHOTOS

The “real” terns weigh 1.4 to 1.8 ounces as adults, which means that at the upper end of the scale, five of them would still weigh less than a regular-size bag of Lay’s Potato Chips (10 oz). The adults are about 9 inches long.

Like a lot of shorebird species, the terns are considered threatened mostly due to habitat loss, often attributed to coastal development, White said.

Least terns primarily nest in large groups, known as colonies, in large, open areas of bare sandy beaches. Do the decoys work? Yes — and no.

“They ultimately decide for themselves where to nest and it is not a guaranteed solution,” White said. “Our wonderful volunteers who helped us paint and place the least tern decoys also helped us set up enclosures around them with stakes, string and signs to prevent disturbance of the habitat.”

Least terns are listed as threatened by the state.

They created an estimated 30 decoys, White said.

Both Weaver and Niesel were part of the group of volunteers that made the birds, painted them and placed them on the beach.

Neither had ever done it before.

“It was kind of a treat,” Weaver said. “Kind of an arts and crafts project.”

Niesel said he had never done much painting — “except for houses.” He helped sketch out the areas on the wooden decoys where the different colors would go.

Both have done volunteer work previously for SCCF – working in the garden center, weeding, and even going out to plant mangroves.

“Every time we volunteer with SCCF it’s fun,” Weaver said.

There are lots of places suitable for the terns to nest on Sanibel and Captiva, but SCCF staff want to get them in an area away from busy beaches, people and dogs. Sometimes the terns decide to nest just outside the cordoned area, which can be frustrating, White said.

Volunteers paint decoy terns.

Other spots are much more problematic. Last year, the least terns tried nesting on the Sanibel Causeway and its islands for the first time in 30 years. That didn’t go well. The bridge and the causeway are under construction due to destruction from Hurricane Ian.

Historically, the terns did nest on the causeway islands, in the ’70s-90s, along with black skimmers, White said. “It was not successful.” As time went on, more and more people brought more and more traffic and their chicks would get hit by cars. So, the terns went elsewhere. Now the expanse of sand as the new construction continues may have enticed them back.

That’s another reason why the decoys are so important.

The terns also nested on Captiva again last year for the first time in 10 years, White said.

If the terns are social creatures, do they try to interact with their wooden counterparts? “Yeah, sometimes they think they’re actual birds,” White said.

One example is courting behavior. A male courts the female with a fish in its mouth, turns its head back and wings spread out, White said. If a male tries to court a “female” decoy, there will be the inevitable disappointment. No matter. The male will just move on to another, hopefully “real” female, and try it again.

White said that nesting as a group allows least terns to communicate more easily and detect nearby threats such as predators.

“Once a threat is detected, least terns collectively start dive bombing and defecating on the threat — yes, really — to drive it away from the colony,” White said. “Threats are not limited to predators such as coyotes or crows, they may also perceive humans as threats, so be wary of incoming airstrikes if you are walking past an enclosed least tern nesting area.”

Wearing a hat — or helmet — might be in order. ¦

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