By Ashley Pickard’s Sixth-Grade Class, National Cathedral School, Washington, D.C.
Editor’s Note: Originally published in the November/December 1996 issue of Dragonfly Magazine, this vintage investigation takes us into the world of an avian predator to see what we can learn from the “leftovers” of its last meal.
The Spark
How can you tell what an owl’s favorite snack is without watching it eat in the dark? We found the answer in owl pellets! We learned that owls usually swallow their food whole. Their stomachs digest the nutritious parts, but they can’t process the “extras”—the teeth, bones, and fur. Instead, the owl spits these leftovers back up in a small, sausage-shaped bundle called a pellet.
We looked at these pellets and asked a big question: Do barn owls have a “strong preference” for certain types of food? Or do they just eat whatever happens to run by?
The Prediction
We predicted that barn owls would show a very strong preference in their diet. Specifically, we thought they would choose small rodents over large rodents or tiny shrews. Our reasoning was simple: small rodents are easy to grab off the ground, they can’t fight back as much as a large rat, and they provide more meat than a tiny insectivore like a shrew.
How We Investigated
Our classroom turned into a forensic lab. Each group received barn owl pellets to dissect. We didn’t just pull them apart; we were careful “bone detectives.” We used a bone chart to identify exactly what we were looking at.
We separated the skulls, jaws, ribs, and limbs from the fur and feathers. Then, we measured the bones to decide if the animal was a “small” rodent, a “medium” rodent, or something else entirely, like a mole or a bird. We pooled our data as a class so we had a larger sample size to look for patterns.
What We Found
When we looked at the class results, we found something surprising! While my specific group found a mix of small rodents, shrews, and even a bird, the class totals showed that the owls actually had more “medium-sized” rodents in their pellets than small ones.
We realized that our original hypothesis—that they preferred small rodents—might have been slightly off. However, we also discussed that we might have made mistakes in measuring, mistaking a small rodent for a medium one. One thing was certain: you can learn a massive amount about an owl’s life just by looking at one single pellet!
Go Wild: Your Turn!
Become a Pellet Detective! You can often find owl pellets at the base of large trees or in old barns.
- The Dissection: If you find a pellet (or buy a heat-sanitized one), carefully pull it apart with tweezers.
- The Bone Count: How many skulls can you find in one pellet? Each skull represents one successful hunt for the owl.
- The Comparison: If you find pellets from two different locations, do the “menus” look the same? Does an owl in the woods eat the same thing as an owl near a farm?
The Field Guide (For Educators)
- Subject/Grade Level: Life Science / Biology / 5th–7th Grade
- Inquiry Focus: Comparative Anatomy, Food Webs, and Data Reliability.
- The Science Behind It: This investigation explores the “niche” of the barn owl (Tyto alba). By analyzing prey remains, students learn about the local ecosystem’s biodiversity. It also introduces the concept of skeletal morphology—using specific bone shapes (like the long incisors of a rodent vs. the teeth of an insectivore) to classify animals.
- Standards Connection: NGSS: MS-LS2-2 (Construct an explanation that predicts patterns of interactions among organisms across multiple ecosystems).
- Materials Needed:
- Heat-sanitized owl pellets
- Tweezers or probes
- Bone identification charts (Rodent, Shrew, Mole, Bird)
- Magnifying glasses
- Small trays for sorting bones