BIRDS AND THE BEES By JACQUELINE BURT WANG July 31, 2004 -- It's the question every child eventually asks, and every parent dreads: "Where do babies come from?" Too bad that stork story doesn't cut it these days - especially in the summer, when a trip to the beach often becomes an impromptu anatomy lesson. Answering kids' queries truthfully, right from the start, will keep the lines of communication open for years to come, says Dr. Justin Richardson, co-author of "Everything You Never Wanted Your Kids to Know About Sex (But Were Afraid They'd Ask)." Here are some tips to get you started. THE AGE OF INNOCENCE (birth to age 4) Think of early childhood as an introduction to the human body. You've already helped your toddler identify her eyes, nose and ears - but what about those "gender-specific" parts? Though it's tempting to use cutesy nicknames, experts recommend sticking to the appropriate anatomical terms, rather than risk being vague or misleading. As TriBeCa pediatrician Michel Cohen puts it, "I think you need to call a cat a cat." As far as those "private" parts go - don't expect your preschooler to keep them so private. Tots have a notorious penchant for taking it all off, anytime, anywhere. No worries: By age 6 or 7, when the "modesty phase" kicks in, she'll be showering with the door closed. In the meantime, set some ground rules. Stripping down is a no-no at dinner - and at preschool, the playground, or anywhere else that's public - but there should be certain times and places (after a bath, say) where it's OK to be in the buff. Kids shouldn't feel as if their naked bodies are taboo; this can lead to low self-esteem. As far as parental privacy goes, it wouldn't hurt to buy a lock for your bedroom door. Of course, should your little one walk in on a romantic interlude, it's not the end of the world. "It really helps to take a moment," says Richardson, an assistant professor of psychiatry at Columbia and Cornell universities. Ask your child to wait outside for a moment while you compose yourself, then calmly escort him back to bed, where you can initiate a brief conversation along the lines of: "When you walked in, Mommy and Daddy were doing a special thing that grown-ups do. Do you have any questions?" (Then pray he'll fall asleep before he thinks of any.) CURIOUSER AND CURIOUSER (ages 4 to 8) Four years old might seem a bit young for a lesson on the facts of life, but experts say it's the best time to learn. "The earlier you do it, the less uncomfortable it is," Richardson says. Besides, if you don't talk to your kids before they're 8 or so, chances are someone else will beat you to it - probably another kid with less-than-accurate information. Don't worry too much about what you're going to say, just tell it like it is, says Cohen, whose book "The New Basics (A to Z Baby and Child Care for the Modern Parent)" extols the virtues of no-nonsense parenting. Be as direct as possible, using simple language children can understand. No need to get too clinical - or too racy. Just the basics will suffice. Don't be surprised if your child's initial reaction is "Yuck." After all, this is the age when many kids think the opposite sex has cooties. Michaele Wylde, a Brooklyn mother of three, says her son, Alex Thomas, 8, was "really grossed out" when he asked for and got the facts of life: "Once was enough, and he's never asked again." At least he'd gotten accurate information. CH-CH-CHANGES (ages 8-12) Hello, hormones. Puberty can start anywhere between 7 and 13 for girls, 9 and 14 for boys. Letting your child know what to expect before the mood swings hit is a good idea, experts say. Even acne is less traumatic if you're prepared for it. Get yourself ready, too: It's not easy when your baby girl starts looking like Britney Spears - or when your son switches from alto to bass. Some fathers withdraw from their daughters during puberty - and even if that's understandable, it's a mistake, Richardson says. It's crucial to keep a close relationship during this time, when girls need all the emotional support they can get. Parents of preteens are often concerned about protecting their children from the barrage of sexual images in the media, but it's impossible to shield them completely - witness Janet Jackson's wardrobe malfunction during the Super Bowl. What's important, he says, is to offer a "competing conversation" about sexuality, so that your child is aware of your morals. The next time you're watching a steamy underage love affair play out on TV, say, "I think those two are too young to get so serious. What do you think?" With a little luck and a lot of humor, you'll survive your child's sex education with your sanity intact. Now get ready for your next challenge: His first date!