The PBS Kids' program “Peg + Cat,” a math adventure series, is aimed at preschoolers through online games and videos. (Feline Features LLC)

On television, Big Bird stands tall among children’s shows. But on the iPad, he is just a little chick.

That dynamic has become a growing worry to the executives of PBS who have a stable of popular educational shows for the living room television but are making far less headway on smartphones, tablets and other mobile gadgets.

On Monday, PBS launched its hope for an Internet hit, funded in part by a $72 million Department of Education Ready to Learn Grant. The program, called “Peg + Cat,” a math ad­ven­ture series, will be introduced to preschoolers through a flood of online games and videos and will eventually make its way into some schools.

With children adopting mobile technology at a breakneck pace and spending immense time on those devices, executives said they have had to broaden their offerings to stay relevant.

“Audience on TV is harder and harder to reach, so the audience on all platforms is critical,” said Scott Chambers, Sesame Workshop’s senior vice president of worldwide media distribution. “Are we gaining a larger audience overall? It’s really hard to say and difficult to track, which is something we lose sleep over.”

Not all are confident that PBS Kids, the network’s educational division, will be able to make the transition.

“The idea of public broadcast was for it to be a TV experience, not a math experience and not a mobile app experience,” said Lloyd Morrisett, chairman emeritus for the board of the Sesame Workshop. “It will be difficult for PBS, as it will for Sesame Workshop, as television organizations to change the culture of those organizations.”

The new PBS Kids series stars a spunky redheaded girl named Peg who the public broadcaster hopes will help ignite the sort of educational revolution Sesame Street did for children four decades ago.

Peg will join a popular children’s lineup on public television that includes “Curious George,” “Clifford the Big Red Dog,” “Dinosaur Train” and “Super Why,” among others.

PBS Kids still has a massive share of the television viewing audience among children. Eight in 10 children ages 2 through 8 watched its shows on TV in the 2011-2012 season.

But that audience that hasn’t grown in five years. And on mobile devices, the network not only faces countless Web sites, but also well-established educational apps and games.

Mobile apps for PBS programs aimed at adults and kids have been downloaded about 9.5 million times, according to PBS (the network did not break out numbers between the age groups). That’s a small fraction of the more than 1 billion downloads for Angry Birds or the more than 100 million downloads of the “Despicable Me: Minion Rush” game by developer Gameloft.

Some analysts say the broadcaster has been slow to boost its online presence and will have difficulty standing out from the hundreds of educational apps crowding the iTunes and Android stores. PBS also competes against corporate giants such as Disney, Fisher-Price and Netflix for a share of the multi-billion-dollar business of entertaining and teaching children online.

With so much competition that’s easily accessible even to the poorest and hardest-to-reach homes in the country, fresh questions have emerged about the future of public broadcasting for children in a smartphone world.

“The justification for PBS children’s grants has run out because there are now so many options available in the private market that are better and more diverse,” said Trevor Burris, a fellow at the Cato Institute. “The initial idea for broadcasting was to respond to a scarcity of spectrum and that there wasn’t enough good children’s content. You can’t say that now.”

PBS executives say their programs have particular appeal on mobile devices because they are well-recognized brands that parents trust.

“We are looking at new technology and apps as an exciting opportunity to reach children and engage them in new ways that ignites passion for learning,” said Lesli Rotenberg, senior vice president of children’s media at Arlington-based PBS.

When Sesame Street first launched, critics balked at the idea of parking children — particularly young kids — in front of television screens. But Sesame Street’s creators said the show filled a gap among low-income working families who struggled to teach the basics of reading and math. The show’s appeal eventually stretched beyond poor homes. Middle-class children also became as enamored with Sesame Street and other PBS shows.

PBS says it hopes it can make a similar foray on mobile devices, even among low-income households. An August survey by the Pew Internet & American Life Project showed 67 percent of families with incomes below $30,000 say they either own a smartphone or broadband Internet connection at home.

PBS Kids’ Martha Speaks and Curious George apps have gained some success and early childhood educators praise the programs for getting preschool children ready for kindergarten. “Peg + Cat” is the network’s first effort to simultaneously release online content and a new TV show.

“Technology can be an equalizer, and it fits with PBS’ mission of creating media for the most disadvantaged kids,” Rotenberg said. “These devices allow children to play in new ways so that you can customize learning and cater to each child.”

The three years of development that went into “Peg + Cat” may help it edge above the competition for the attention of parents and children, some educational experts say.

“Whenever PBS or Sesame Street Workshop creates a new product, it puts its writers through a ‘curriculum bath’ so they are soaked in research and have the foundational knowledge to build upon,” said Michael Davis, author of “Street Gang,” the history of Sesame Street. “I’m rooting for PBS Kids and The Workshop because they are still creating such high quality material.”

Peg and each of her math adventures were developed with guidance by education experts, behavioral scientists and artists. The advisers made fixes on math concepts and made sure the show followed Common Core guidelines being taught in schools.

Both the television show and the online experience uses proper terms that will show up later in a child’s education. For instance, creators of the online game “Magical Shape Hunter” avoided using the term “oval,” which doesn’t have a precise definition and is not typically used in math classes.

“I asked the show’s creators to make sure to include shapes that have a clear definition,” said Francis “Skip” Fennell, a professor of education at McDaniel College and former president of the National Council of Teachers of Mathematics, who was a paid adviser to the “Peg + Cat” programs.

“These may seem like silly changes, but they aren’t silly at all. Getting the vocabulary right is important because if you get it right the first time, it becomes easier for the student in the third grade to build on it,” Fennell added.

Follow The Post’s new tech blog, The Switch, where technology and policy connect.