Which Senses Do Robins Use to Find Worms? Dr. Heppner's Experiment Looking, smelling, running, listening. Robins spend much of their lives searching for one of their favorite foods: earthworms. How DO they find them? Photo Wayne Kryduba Investigating a Robin's Senses An ornithologist named Frank Heppner wanted to know the answer to that question. He set up some experiments, knowing he would need to investigate all the robins' senses. This is the equipment he used: Pieces of dead earthworm Living earthworms Rotten eggs Decaying meat Rancid butter Mercaptoacetic acid (which smells like a cross between sewer gas, rotten cabbage, a skunk, and a stinkbug) A small drill A tape recorder that was extremely sensitive at low frequencies If you had the materials Frank Heppner used, how would you design experiments to prove which sense(s) robins use to find worms? Why do you think he used each of these materials?" Several students from Ms. Sheer's fourth grade class at Glenwood School in Chapel Hill, North Carolina, pondered this question long and hard and came up with some fabulous experimental designs. Some were exactly what Dr. Heppner had thought of; others would make fascinating experiments, too. Do you have additional ideas? Below you'll find the 4th graders' suggestions, organized by the five senses, along with Dr. Heppner's conclusions. Experiments and Conclusions HEARING The class suggests: "The tape recorder can pick up very faint noises so the person starts the drill at low speed. The tape recorder catches the noises and puts the noise near the robin. It might hear the little noises and go down and look at the tape recorder, thinking it is a worm." Dr. Heppner's study: That's exactly what Dr. Heppner did. Using VERY sensitive recording equipment, Dr. Heppner taped the low-frequency sounds made by burrowing earthworms. He found that robins ignored the sounds. SMELL The class suggests: "Mercaptoacetic acid smells really really bad, so the worms are attracted to the smell and robins will smell the scent and go down to where he smelled the smell and dig." Alternatively, "The scientist might put a living earthworm close to a robin, and if it comes down to get it, you will know that the robin is either using its sense of smell or its vision. The scientist might take another earthworm, cover it with one of the smelly substances and then put it at the same distance from the bird. If it comes down, it was probably using its vision. If it doesn't, it was using its sense of smell." Dr. Heppner's findings: We don't know if worms are attracted to mercaptoacetic acid, but Dr. Heppner recorded that "robins nonchalantly ate foods smelling like rotten eggs, decaying meats, rancid butter, and the absolutely worst smell of all bad smells: mercaptoacetic acid." He concluded that robins don't seem to notice that nice wormy smell at all! TASTE Robins would have to taste a LOT of dirt to pick out worms this way! So neither Dr. Heppner nor Ms. Sheer's class even considered this possibility. TOUCH The class suggests: "If robins feel vibrations of live, wiggly worms, they wouldn't bother eating still, dead worms. Use dead earthworms and live earthworms to see what robins will go to. If they go to the live ones, they are probably using their sense of vision because bits of dead earthworms don't look like live ones." Dr. Heppner's experiment: When he drilled worm-like holes in the ground and placed dead worms in them, the robins peeked in the holes, found the dead worms, and ate them readily! Do you think robins would eat dead worms just laying around on top of the grass? That would be an easy experiment to try. VISION (the conclusion!) When Dr. Heppner drilled holes that looked exactly like wormholes, robins ignored the holes UNLESS a worm was in them. Whether that worm was alive and normal, alive but coated with a bad-smelling odor, or dead, the robins found and ate it. He concluded that robins look for earthworm holes that have a worm within visual range. Try This! Journal Questions Why does a robin seem to have to tug so hard to get a worm out of the ground? Do some research about worm anatomy as you dig into the answer for this question. (Visit the home page of the Earthworm on Journey North for links.) What might be the reason for a robin's feeding pattern of hunting for worms in early morning and late afternoon — and eating fruits, spiders and other small creatures at mid-day? What did you learn from this activity about how scientists try to find answers to their questions? National Science Education Standards >>   This Season Teachers Kids Orientation Registration Search Copyright 1997-2008 Journey North. All Rights Reserved. Questions or comments? Contact us.