There's a troubling pattern in children's books: When the characters are not human, as is often the case, females are often strangely absent.

I am not splitting politically correct hairs. "Chick 'n' Pug," a 2010 book by Jennifer Sattler, was my tipping point. The main character is a baby chicken who wants to avoid a life of "laying eggs all day" and sets off to find adventure with "Wonder Pug," a male. The feline antagonist is male, too. But the kicker? The would-be egg-laying chick is also male. And, no, this is not a story about gender confusion. There is no rooster reveal later in the book. This oversight on the part of the author, editors and publishers would be laughable if it weren't so disturbing.

Authors lend everything from beavers to bulldozers big personalities and adventures, but rarely give them a female pronoun. After I discovered the discrepancy in "Chick 'n' Pug," I tore through every book on my daughter's shelf. I examined the first 50 published in the past 10 years, and tallied every nonhuman character: 45 female and 104 male.

One 2011 study confirms that I'm not imagining things: In 5,618 titles evaluated, nearly twice as many males are depicted as females. According to the study, rates are even worse where animal characters are concerned.

I'm no scientist, but I believe females account for about 50 percent of the planet's population. So where are we in books that make up our children's earliest literary diet? If girls have challenges with self-worth, it can't help that the stories they hear from infancy ignore their very existence.

Females do abound in the form of mothers. For example, Eve Bunting's new picture book "I'm A Duck" tells the tale of a duck afraid of water. The scared duck's sex is ambiguous, but five other creatures are identified as male. The lone female is, as usual, a mother on the sidelines.

And if the characters are engaged in social drama, they're a mix of girls and boys, whether humans or llamas. But if the story involves industrious skunks or adventurous appliances, females are often missing. Sadly, the conditioning is so strong that the authors guilty of this imbalance are often women.

Another distressing example is "A Sick Day for Amos McGee," written by Philip C. Stead and illustrated by Erin E. Stead. The 2011 Caldecott Medal winner honors friendship and empathy with gorgeous prose and artwork. It was one of my favorites until I realized: The human zookeeper's friends — a tortoise, a penguin, an elephant, an owl and a rhinoceros — are all male. My blood pressure rose as I read one single page with a series of "him's" and "his's." If creators as thoughtful as the Steads could write a book lacking a single female character, we clearly have a problem.

Authors need not manufacture a flood of "girl power" books and stories subverting the old princess theme. The solution can be more natural, and therefore more powerful: Just take a whole bunch of "he's" and turn them to "she's."

Many parents are already working to do just that in their daily lives. When my husband or I see a caterpillar outside, we're as likely to say, "Look at how fuzzy she is!" as we are to say, "He is."

Too many book publishers have not thought to do the same, despite the rounds of editing that their stories undergo. But some authors have overcome the male assumption. "A House in the Woods" by Inga Moore, for example, left me stunned with gratitude as I read it to my daughter. Two of the four main critters are female. They help to build a house and are drawn like any other pig or bear.

So thank you, Inga Moore, Mo Willems, Tad Hills and others who are bucking the trend. To parents and educators, remind your favorite authors that half of all squirrels and rhinos have two X chromosomes. Stop buying books that portray a weirdly imbalanced world. To authors and publishers who have not realized the power of pronouns, who might even forget who lays the eggs, get with the program.

Christine Michaud Woods is a writer living in South Berwick, Maine. She wrote this article for the Washington Post.