Oh, dear. Does "working mom" in picture books mean "absent mom"? Owl Babies sounds lovely, but as a working mom myself, I hate to think that the absent mom is the best we can come up with in that category.
That said, only two picture books spring to mind for me. The first is I Live in Brooklyn, which we have been given no less than three times because, well, we live in Brooklyn. (At some point, I'd love to do a post on place-specific books, so many of which are deeply dull.)
Still, Michelle's mother works! Every morning, she leaves Michelle's sister Lucy with their grandma (who conveniently lives one block away, sigh), and takes the bus with Michelle: "She drops me off at school and then goes on to her office." No drama, no emotion, just simple fact.
The other book that came to mind after reading your post isn't really about a working mother, but another animal mother who leaves her kid alone to go forage for food. It's one of my all-time favorite children's books, however, so I'm going to seize the opportunity to write about it.
Wait Till the Moon is Full is Margaret Wise Brown at her best:
Once upon a time in the dark of the moon
He lived down in a big warm chestnut tree
with his mother -- who was also a raccoon.
This little raccoon wanted to see the night. He
had seen the day.
So he said to his mother, "I want to go out in the
woods and see the night."
But his mother said, "Wait."
"Wait till the moon is full." So he waited, deep
in his warm little home under the chestnut tree.
As the raccoon waits and grows, and the moon waxes, he hears the sounds of the night, and his mother tells him to wait, and sings him songs about the night. On one page, his mother is late coming home, and the raccoon "sat there wondering to himself." But then she returns, "skuttle bump, in came his mother, her pointed ears pushed back on her head" (and, in the Garth Williams drawing, in a shawl and carrying a basket of groceries). And of course, eventually, the moon is full, and the little raccoon gets to go out and play in the moonlight, and the waiting is rewarded.
As ours will be starting tomorrow with our week of family weddings! See you then.
Love, Annie