image of robin with earthworms in beak

American Robin. Photo by Brocken Inaglory. Creative Commons Attribution Share Alike 4.0 International license.

Next time you see a robin on your lawn, take a look at how it catches worms. At times it will appear to cock its head and listen to the ground. Naturalists have suspected since the 1800s that robins can actually hearworms moving beneath the soil. Years ago, two Canadian biologists devised a series of experiments to test the theory.

“Well, we caught a few robins,” recalls Bob Montgomerie, who worked on the study with Patrick Weatherhead. “We were working on them anyway. We were studying the way that they look after their babies and choose mates. And so we grabbed a couple and put them in an outdoor aviary that we had at our field station. And then we designed a careful experimental protocol to try to eliminate each of the sensory modes in order.”

They hid worms behind barriers. They eliminated the possibilities of smell and touch. But just based on hearing, robins “found the worms with no problem,” says Montgomerie. While visual cues remained important, the birds had significantly less success if they could not use their hearing, according to a report by the scientists in the journal Animal Behaviour.

Just how a robin is able to hear something as quiet as an earthworm is still unknown, but they are not the only birds that can locate food this way. Magpies are also known to locate scarab beetle grubs in the ground through hearing.

Listen to a version of this story on the public radio program Living on Earth. 

Hear the sound of an earthworm on the MSU library’s Acoustic Atlas.