Christopher Heib rises before dawn to get to his day job as a power line worker for the Los Angeles Department of Water and Power. But just as important to him is his second shift-- taking care of his sons Rudy, 6, and Thomas, a newborn.

Like many other men his age, Mr. Heib, 33, of Long Beach, Calif., regrets having spent so little time with his father growing up. But unlike fathers who hold professional of managerial jobs that occupy them 50 or more hours a week, Mr. Heib's job allows him the flexibility to be the father he wishes he'd had.

"I like coming home to take care of the kids," said Mr. Heib, who takes over at 4:30 p.m. when his wife, Sandra, 31, leaves for her job as a 911 dispatcher for the Los Angeles Police Department. Her shift runs from 6 p.m. to 2:30 a.m. "I feel I can talk to my son. He's closer to me than I was to my parents. I can come home every single night and be with him."

The number of children being cared for by their fathers is "the best-kept secret in American child care," said James Levine, author of "Working Fathers" (Addison-Wesley, 1997) and director of the Fatherhood Project at he Families and Work Institute in New York.

Moreover, it is not upper-middle-class professionals or corporate managers who are leading the trend toward more involved fatherhood; it is lower-paid, blue-collar men. "Most people think of the stereotype of Mr. Mom, the guy who quits his job and stays home," said Mr. Levine, "when in fact most guys who are primary care givers are in families with two working parents on split shifts."

In 1993, among all married fathers of children younger than age 5, some 1.6 million-- about 25 percent-- cared for their children while the mothers worked. In service occupations, the numbers were far higher: 42 percent of fathers cared for preschoolers, the Census Bureau found, versus 20 percent of fathers with professional or managerial jobs.

And the demands of work and home take a toll, too. Lonnie Morgan, 31, a correction officer in Madison, Wis., notes a lake of time for himself. He works a 3 to 11 p.m. shift and cares for his son Joshua, 4, and daughter Moriah, 3, while his wife Debora, 29, works as an officer manager from 6:30 a.m. to 1:30 p.m.

"All I do is watch the kids and work," Mr. Morgan said. "There is no time to go out and play tennis or see friends." He has a new appreciation for all that child-rearing entails: "I understand how frustrating it can be. You're not just sitting around watching soap operas."