The incident, in 2009, naturally drew headlines. While there had always been turtles in the Jamaica Bay Wildlife Refuge, just south of Kennedy Airport, their occasional presence on the airport’s grounds did not normally cause a stir.

But on that July day five years ago, Russell Burke, the chairman of the biology department at Hofstra University, said, “Something made a huge number of turtles come up to Runway 4L.”

Two years later, it happened a second time. And on Thursday, a group of turtles appeared on Runway 4L yet again, despite recent steps aimed at keeping them away.

For Dr. Burke, who has long studied the terrapins that live in the wildlife refuge, the reptiles’ repeated forays onto the tarmac are the subject of serious study. Shortly after the first invasion, the Port Authority of New York and New Jersey enlisted him to help it come to a better understanding of the turtles and their mysterious ways. As part of that effort, he works closely with the Port Authority’s chief wildlife biologist, Laura Francoeur, who described the turtle takeovers as among the more vexing challenges confronting her unit.