Tina Chen has her hands full as a New York City actress, director and now surrogate mother to 16 ducklings that have hatched on her high-rise apartment roof deck. Local mallards, seeking safe spots for their nests, have an eye for prime real estate and often nest on high floors on Manhattan's affluent Upper East and West sides, experts say. These 16 baby birds born a week ago, are enjoying the hospitality of Chen, whose 12th-floor deck between Madison and Park Avenues has been home to wild ducklings for the last four years. They are the first of what is likely to be as many as ten broods born this season high atop New York City buildings, wildlife experts say. true Chen is feeding them meals twice a day of duck pellets and shredded greens, putting out water for them to swim in and cleaning up after them, which she says is no small task. "It's really a lot of work. The poop out there is tremendous," she said. "That's a lot of ducklings." M