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Who'd have thought?
Actually it's probably more correct to say that they listen FOR worms - it is how the red breasted birds locate their favorite, free-range, organic, underground food and the reason that the robins tilt their heads to the side just before they thrust their pointy little beaks into the moist earth.
The program played a tape of those noises that was recorded with a high-sensitivity directional microphone in an an anechoic chamber (a room that is isolated from external sound) . They were barely audible. In fairness to the worms and the scientists I was lying in bed trying to wake up when I heard this, with my hearing not functioning at its best - or at least the portion that involves ear to brain conversations.
Also I didn't really expect be listening to worms at that early hour. Robins maybe, but not worms.
Now this is not underground singing, or rhythmic chanting, or communication of any recognizable form. So do not go looking for any "Songs of the European Nightcrawler" or "Red Wiggler's Greatest Hits" albums anytime soon. The worms apparently make these noises when their slimy, slithering bodies cause the particles of sand in the soil to hit up against each other. I guess technically this makes them "sounds made as an accidental byproduct of the movement of burrowing invertebrate animals with long, slender, soft bodies and no limbs" - perhaps a good name for a scholarly work but definitely not a smash CD title.
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Somehow I'm not that stunned that robins can hear worms. Having once had a Labrador Retriever/Irish Setter cross for many years I am well aware of some animals' ability to tune in to sounds and smells that just don't exist in the world of humans.
Worms do not have ears. But still I'm surprised that they can't hear the robins. I mean I can make them out just fine - especially early in the morning when I am trying to sleep. At daybreak there is nothing more annoying than that large thrush's sarcastic rendition of the classic "cheerily, cheer up, cheer up, cheerily, cheer up" melody with a background chorus of "chup...chup...chup" provided by its fellow redbreasts.
I am reminded of a "poem" from my youth:
"A birdie with a yellow bill
Hopped up on my windowsill
Sang "Hey get up, get out of bed."
I closed the window and crushed its head."
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Maybe these same scientists should study the effects of robin songs on the rest of the world. They could start by putting the birds in the same soundproof chamber that they used to amplify the worm noises. And then leave them there until the rest of us get ourselves at least a couple of good nights' sleep.