Robins run very intently across the lawn, cocking their heads, pausing frequently and eventually pulling long earthworms right out of the soil. But how do robins find worms and strike them so precisely, when the birds aren't digging around constantly?
Why Eat Worms?
Worms are the ideal food for omnivorous birds such as robins and other thrushes. While birds will eat just about any type of worm they can catch, earthworms and insect larvae are the most common worms they eat. An American robin, in fact, may eat up to 14 feet of earthworms in a single day, and worms make up 15-20 percent of its summer diet.
While the exact nutritional composition of different worms will vary, they are all generally high in protein. This is essential for birds to develop strong muscles and feathers, and is especially critical for growing chicks. Worms are also good sources of fat for energy, as well as a variety of vitamins and minerals, including…
These are all necessary parts of a healthy diet for birds, and worms meet those dietary needs very well.
How Robins Locate Worms
Robins and other birds use all their senses for successful worm-finding. It is likely that individual birds rely more heavily on different senses depending on their needs and abilities as well as the worm-hunting conditions. Several research studies have been conducted with different bird species to determine their ability to locate worms with different sensory detection methods. The most important senses for finding worms are…
- Vision: Birds, including robins, find worms mostly through sight. Birds have exceptional vision, and their keen eyes can see the tiny end of a worm as it may poke out of the dirt. They can also see small changes in soil and grass as worms move about just below the surface, movements that indicate where a worm is. Songbirds have monocular vision – each eye can operate independently – so when they cock their heads to the side, they are actually turning one eye to look more closely at the soil. When they see a worm, they strike!
- Sound: As worms move about, they disrupt the soil and small particles of dirt rub together, making noises too faint for humans to hear. Birds have a much better hearing, however, and it is possible that some noises can be part of how robins find worms. This is only a minor use of their hearing, however, and detailed studies have not proven that any birds can find worms by hearing alone.
- Touch: Another possibility for how robins find worms is by touch, as they can feel a worm's subtle movements in the soil beneath their feet. The upheaval of the soil or the gentle movements of grass blades disturbed by worm activity could alert a nearby bird, leading to a successful worm hunt. Like hearing, however, it is unlikely that the sense of touch is critical for a robin's worm-hunting abilities.
The remaining senses – smell and taste – are not useful as robins hunt worms. Most birds, including robins and other songbirds, have very weak, insignificant senses of smell and taste, and these senses would not be needed for finding worms. From different laboratory studies as well as casual observations of foraging robins, it is clear that vision is the most important sense birds use to find worms.
Helping Robins Find Worms
Backyard birders can help robins, thrushes, starlings and other worm-eating birds find their next mouthful with ease. To help birds find worms…
- Keep the lawn evenly trimmed with shorter grass. This makes it easier for birds to see the soil and note where worms may be moving, as well as easier to reach their next bite.
- Water lawns in the early morning. This will bring worms closer to the surface or even encourage them to emerge from the lawn, making these tidbits more accessible to hungry robins.
- Keep the lawn in good condition with yearly aeration and thatch removal. This will make it easier for birds to reach the soil and remove worms from looser, less compact dirt.
- Avoid using weed fabric or other coverings in garden areas or flower beds where robins may be hunting. Birds cannot easily poke through these covers even when they find worms.
- Leave fallen leaves intact for birds to forage through. The damp, organically-rich soil under leaves and wood mulch is ideal for worms and easier for birds to find tasty morsels.
- Offer mealworms in low tray feeders or small dishes at a bird feeding station. Robins, catbirds, bluebirds and other worm-loving birds will appreciate the easy treat.
Robins are very adept at finding worms, and birders who understand just how they do it can take steps to help birds find bigger, juicier, more nutritious worms in the backyard.