Corvid cleverness is making news lately. Two of my favorite science writers, Sharon Begley and James Gorman, describe a variety of experiments—reported in PLOS One by researchers in New Zealand--in which crows mimic the hero of Aesop's ancient fable "The Crow and the Pitcher." By dropping objects into containers of water, crows raise the water's level so they can snatch floating food. Most human kids can't solve this problem until they are five or older.

I used to be married to a woman who nursed injured and orphaned birds before releasing them back into the wild, so I have first-hand experience of crows' intelligence—and sense of humor. Take, for example, George, an orphan whom Suzie, my ex-wife, raised a dozen summers ago.

After George mastered flying indoors, Suzie released him outside. Like many birds she raised, he was fond of his human family, so he hung around for a while. George was mischievous, as corvids tend to be. If I was outside, cutting the lawn, say, George liked to fly straight at my face and veer away at the last second as I flinched. If I sat on the deck overlooking our lawn, reading a newspaper or eating lunch, George got a kick out of swooping down on me to peck at my food or newspaper.

One day I was in the house and heard all this yelling outside. I went downstairs and found Suzie and our two kids—Mac, who was eight, and Skye, seven—milling around outside the big bird cage in our backyard. The cage was a cube, eight feet long on each side, made of wood and chicken wire.

The cage had a door with a bolt latch on the outside. Mac and Skye often locked each other inside the cage for fun. Mac and Skye claimed that they had been playing in the cage when George had shut the door behind them and locked them in. Suzie, hearing Mac and Skye yelling, had just unlocked the door and let them out.

As Suzie, Mac and Skye told me this tale, George stood on the grass watching us with his head cocked, looking pleased with himself.

I nonetheless found the story hard to believe, especially since my wife and children liked to kid me. So I sent Suzie, Mac and Skye to the deck, about 30 feet away. Then I entered the cage. I turned my back on the door and on George, and a moment later I heard wings flapping. I turned just in time to see George fly up to the middle of door, which I had left ajar. He hooked his talons onto the chicken wire just below the door's latch, flapped his wings until the door eased shut and slid the latch over with his beak, locking me in. Then, I swear, George grinned.

The cognitive talents of crows raise questions about the evolution of intelligence, and "suggest that an understanding of cause and effect evolved fairly early," as Begley puts it.

Hanging out with George and other crows makes me wonder as well about the evolution of humor. Is humor a case of convergent evolution, a trait that evolved independently in separate lineages? And if so, is humor a spandrel, a non-adaptive side effect of intelligence, or did it originally serve some reproductive purpose?

The philosopher David Rothenberg has suggested that birds sing not just to attract mates but for fun. Perhaps crows goof on other creatures for the same reason.

Illustration of "The Crow and the Pitcher" by Milo Winter, 1919, from Wikimedia Commons, http://en.wikipedia.org/wiki/File:The_Crow_and_the_Pitcher_-_Project_Gutenberg_etext_19994.jpg.