More than 400 bird-watchers turned up at the crack of dawn at a sewage plant to get a glimpse of an apparently disoriented arctic bird rarely seen south of Canada, a Ross's gull. ``I woke up at 4:15 to come out here,'' said George Armistead, 16, of Philadelphia. ``I never thought I'd see the day when a Ross's gull would land so close I could make the drive in a little over two hours.'' At 8:35 a.m. Sunday, someone finally spotted the gull in flight. It eventually settled down to preen for a half-hour near a creek behind the Back River treatment plant in suburban Baltimore. ``What makes this Ross's gull so unique is that every other past record has been a one-day wonder,'' said birdwatcher Rick Blom. ``This Ross's gull has already been in Baltimore for more than a week.'' Blom said the gull is a long-distance migrator that has a tendency to get blown off course. The first confirmed U.S. sighting of a Ross's gull was believed to have been in 1975 in Salisbury Beach, Mass. Unconfirmed sightings have been reported as far afield as Tennessee and Colorado.