Groton - If the current forecast for sunny weather Tuesday proves correct, Groton-New London Airport that morning will be the scene of a military mission with an environmental purpose.

At the request of the U.S. Fish & Wildlife Service's Charlestown, R.I., office, the Connecticut Army National Guard will airlift 28,000 pounds of lumber to Great Gull Island, a bird sanctuary in Long Island Sound between Plum and Fishers islands.

"We have accepted that mission," Col. John T. Wiltse, director of public affairs for the Connecticut National Guard, said Thursday.

A CH-47 medium-lift Chinook helicopter will make three trips to the island to transport the lumber, Wiltse said. The island is about 8 miles from the airport, he said, and each round trip is expected to take 45 minutes to an hour.

Helen Hays, manager of Great Gull Island since 1968, said the lumber was purchased with a Fish & Wildlife Service grant and will be used to create nesting areas for roseate terns as well as 20 bird blinds from which she and other wildlife biologists and volunteers can observe them.

With 1,500 nesting pairs of roseate terns, Great Gull supports the largest colony of the endangered birds in the Western Hemisphere, Hays said Friday. Many of the rock crevices and other areas on the island used by the birds were overwashed during Superstorm Sandy, she said, forcing the birds to move to other areas. It also destroyed most of about 30 blinds that had been built there.

"Last summer we had birds flying over all summer looking for places to nest," Hays said. "There are always more pairs looking to nest than there are nesting sites."

The island also hosts 9,500 pairs of common terns each spring, making it the world's largest nesting colony for that species, Hays said.

Sandy also destroyed the dock on the island and caused severe erosion of some of the beaches. The only way to get the lumber needed for the project to the island is by helicopter, Hays said.

The 17-acre island has been owned by the American Museum of Natural History in New York City since 1949. The long-term monitoring, banding and counting of the birds there has produced some of the most comprehensive data on nesting terns.

"We're trying to create more habitat for the roseate terns, so we're using the lumber to terrace some of the areas where there were gun emplacements," Hays said, referring to the structures left from when the island was used by the Army from the Spanish American War through World War II.

Matthew Male of Chester, a volunteer and consultant at Great Gull, will supervise the building of the terraces and new blinds. He had built most of the 30 that were destroyed by Sandy. Preserving and enhancing the nesting areas on the island is critical to the survival of both species, he said.

"I started volunteering there around 1973 or '74, and every year I try to get out there," Male said. "One-third of all the common and roseate terns that breed on the East Coast have some link to the Supercolony on Great Gull Island."

With the birds scheduled to arrive at the end of this month for the start of the nesting season, Hays said, the deliveries must be completed next week to avoid disturbing the terns. Some construction will begin as soon as the lumber arrives, she said, but most of the work will wait until the fall after the birds migrate south for the winter.

"It's really wonderful of the National Guard to do this," Hays said. "I can't tell you how relieved we are that they've agreed to do this. We're certainly grateful."

j.benson@theday.com