oystercatcher nest

An American Oystercatcher with its chick on a Charleston parking garage in May 2019. Ray Swagerty/Provided 

A pair of shorebirds has hatched chicks on a downtown Charleston rooftop for the third year in a row, a rare occurrence for the typically beach-going species, a biologist said. 

The American Oystercatcher chicks have struggled in an urban environment in all three years, and their parents' selection of a rooftop shows the pressures on their natural habitat.

Ray Swagerty, who works for the city of Charleston at 75 Calhoun St., has been watching the nest since 2017 when the two shorebirds first scraped a small home out of pea gravel. Though the nest was on top of his building, he spotted it from a parking garage next door. The site is near the Gaillard Center.

"I thought it was a little strange and I contacted the Department of Natural Resources, and they basically said they don't nest on roofs in South Carolina, normally," Swagerty said.

Swagerty already recognized the species because he's an avid birder in his off time — he leads a volunteer count of fowl at Magnolia Plantation on the weekends. 

The Oystercatcher, with its black head, long legs and brilliant orange beak, relies on sandy areas with plenty of bivalves — oysters, clams, mussels and scallops — nearby. They prefer a full range of vision because they will flee from potential threats, said Mary-Catherine Martin, a biologist with DNR.

There are many rooftop nests in Florida, Martin said, because of developmental pressures on the beaches there.

The cases of rooftop nests are far rarer in South Carolina, with only two other cases about six years ago on S.C. Ports Authority buildings near the harbor.

As the pair on Calhoun Street returned year after year, the results were mixed. The birds hatched two chicks each year for the past two years, but only one may have survived in 2017.

In 2018, one chick died relatively young. The other lived long enough to be sent to the Center for Birds of Prey in Awendaw, but later died there.

This year, the pair laid three eggs. One chick died about 10 days after hatching, which is common in nests of three, Martin said.

Another was spotted by Swagerty flying "like a fighter pilot" with one of the parents. However, that bird was later found on the street with a hurt foot. It was taken to the Awendaw center and euthanized because its foot injury could not be fixed. 

The third bird lingered on the ground around the Galliard Center for weeks.

"It crossed Calhoun Street a couple of times in morning rush hour to go to the library," Swagerty said. "I don't know why, but it didn't get hit."

It also ended up at the Birds of Prey site and is awaiting transfer to another facility, Martin said, potentially the S.C. Aquarium. 

That bird will have to live in captivity for the rest of its life because Oystercatchers have to learn their foraging techniques from their parents. Since the chick was unable to make it to wherever its mother and father were getting food, Martin said, it wouldn't be able to feed itself as an adult. 

A roof isn't ideal for other reasons: Oystercatchers don't nest on cliffs, so they may fall off the side of a building, Martin said.

Even that relatively poor urban environment is going away. Martin primarily studies another seabird, the Least Tern, which nests on rooftops more often than Oystercatchers. In the five years she's been tracking terns, the pea gravel they use is going away. It's the same type of roof the Oystercatchers selected.

It's an outdated form of construction, and the birds can't nest on modern membrane-covered roofs. The better option, Martin said, is to preserve or improve natural habitats. 

"These birds are so driven to follow through that instinct that they'll look for a place to do this," she said. "That's why setting aside places for them is so important."

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Reach Chloe Johnson at 843-735-9985. Follow her on Twitter @_ChloeAJ.

Chloe Johnson covers the coastal environment and climate change for the Post and Courier. She's always looking for a good excuse to hop on a boat.

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