Actress Kristy McNichol won’t fly the coop exactly, but she will be taking an open-ended hiatus from the veteran NBC series “Empty Nest,” exec producer Tony Thomas confirmed yesterday.

McNichol is taking the break on the advice of her doctors, having dealt for some time with a bi-polar condition, the producer said, which can lead to exhaustion and other problems.

“Empty Nest” has completed about 10 episodes of this season’s order with McNichol and has a two-year commitment from NBC. Thomas said he’s hopeful the actress will be back before the end of this season but stressed that her health remains the first priority.

In the interim the producers plan to say her character, a policewoman, is on assignment undercover and possibly bring in an off-camera third daughter that’s been referred to throughout the series but never seen.

McNichol and Dinah Manoff play the daughters of Richard Mulligan on the show, which also stars David Leisure, Park Overall and new cast member Paul Provenza.

“Nest” has premiered solidly in its fifth season, averaging a 12.9 rating, 24 share nationally for its first two airings, down somewhat from last year’s average but still dominating its time period.

McNichol has been on the Witt-Thomas-Harris/Touchstone TV sitcom since it premiered. She co-starred for five seasons, from 1976-80, in the drama series “Family.”

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