Earth Worms on Earth Day: Evolutionary Pressures at Work?

Back in days of real, live switchboard operators, I once interviewed an ”Information” lady at McGill for story about non-academic employees for the university’s alumni magazine. "Information," you’ll recall, was whom you called to get a telephone number, but people obviously saw the question as much larger. She got some good ones, she said, and probably the best—and most puzzling—was “Does it really rain worms in the spring time?”

I thought of that this morning on my walk in Mount Royal cemetery. After 36 hours of rain, I saw a half dozen earth worms slowly making their way across pavement. Somewhere along the way I was told that worms must come up for air when the soil is saturated, so I presume that these ones had been flooded out. But why does this happen in spring and not later on when rain from thunder storms surely must fill their tunnels too?

Then I saw one of the first robins of the season, and it came clear. During the summer, worm-loving birds feeding their young and then getting ready for migration must pounce upon any worm that finds itself out n the open. Right now there are fewer predators so the chances of survival on the surface after a rain goes up.

I didn’t stick around to see if the robin found the worms, though. Too sweet an Earth Day morning to watch nature red in tooth and claw work through the evolutionary drama.