Two silver gull cases were also detected on the Limestone Coast, at Port MacDonnell and Robe. "Unfortunately, we were just unlucky to be the first place where this did spread into our resident birds," she told ABC. "The (terns) are a local species that move up and down our coast from Portland, Yambuk to Port Fairy. They move, separate and nest together," Ms Gray told AAP. "We're really challenged at the moment because we know the vastness of the coast area," Ms Gray added.