Mallards and ducks roost among the lush lawns of the 28-acre park. In springtime, furry ducklings follow mommies around and take a taste of water at the park's lagoon. Every summer, quacking punctuates the witty lines of Shakespeare's plays and creates background sound effects for other events at the park. In winter, migratory geese flock here.

"The number of birds at Memorial Park fluctuates throughout the year," said Bob Rizzo, who manages the city's facilities, including parks. "It is not uncommon that we have 200 to 300 migratory birds staying here in winter. Some of them even become domestic and don't migrate."

The birds, no matter how cute they look, have become a burden for the city's park maintenance crew, Rizzo said.

"The water gets so dirty that we have to drain the lake three or four times a year," Rizzo said. "This year we have to drain the lake at least four times."

The Bay Area's warm climate, the lack of predators in the park and people feeding the birds are some of the major reasons why Memorial Park is a sanctuary for birds, Rizzo said.

"Cupertino doesn't have an ordinance to forbid people from feeding birds, so people continue feeding the birds although there are signs requesting them not to," Rizzo said.

Jennifer Peritz (pronounced parrots), program coordinator of Cupertino-based Santa Clara Valley Audubon Society, said although people think feeding birds is a fun and helpful thing to do, it can be harmful for both people and birds.

"While it may be helpful to offer appropriate bird feed as an additional food source, wild birds don't eat bread," Peritz said. "When you introduce alternative food, you are stopping them from eating what they normally eat. The bodies of most ducks and geese are designed to eat vegetation and grass, not bread."

Feeding birds also causes the birds to rely on humans. "When the adult birds raise their young, the chicks follow the adults' behavior and learn to depend on human beings," Peritz said.

What's more, feeding birds can be dangerous, Peritz said. "People forget that these birds are wild animals. We cannot predict their behavior," she said. "Canada geese are especially aggressive and territorial when fighting for food."

Cupertino is not alone in dealing with bird overpopulation. The federal government recently proposed allowing states to kill Canada geese, which have become an increasing nuisance in urban recreational areas. The city of Fremont just bought a McNab shepherd dog, whose job is to chase the geese into the water at Lake Elizabeth Park.

The city of Cupertino is exploring options to control the bird population, but no decisions have been made so far.

"Right now, all we can do is educate the community not to feed the birds," Rizzo said. "People must remember that what goes in must come out."