The end may be nigh for Berkeley’s celebrated burrowing owls. Despite extensive efforts to protect the migratory birds’ overwintering habitat at the Berkeley Marina — including a $6 million, five-year restoration of the Berkeley Meadow and the installation of a $100,000 art project at Cesar Chavez Park designed specifically to protect the owls — their numbers continue to drop. This winter, only two owls have been spotted in the area, down from six last year and as many as fifteen a decade ago. A thorough survey of the meadow’s 72 acres in January, however, could potentially turn up more, said Golden Gate Audubon Society volunteer Della Dash, who leads the Marina’s owl docent program. “The meadow is really great habitat for the owls right now, especially since they finished the restoration,” she said. However, none have been spotted there this year.