What 453 Owl Pellets Can Tell Us About a Habitat

Winter (and early spring) has a funny way of turning the outdoors into a science lab. You don’t need a microscope. You don’t need a fancy field station.

Sometimes you just need a pellet.

In a study with Kim Regier, EdD (Department of Integrative Biology) at the University of Colorado Denver, students have been collecting data from barn owl pellets from OBDK since 2020. After 453 pellets dissected, here’s what showed up as the top prey categories:

• Voles: 507
• Mice: 329
• Rats: 223
• Birds: 128
• Shrews: 121
• Moles: 95
• Insects & other: 67

That’s not just a list of animals. It’s a habitat fingerprint—a picture of what’s living nearby, moving under cover, and getting hunted after dark.

The Big Idea: Pellets Are “Inside Evidence”

Tracks tell you what happened on the surface.

Pellets tell you what happened inside the food web.

Each pellet is a compact data packet: fur, bones, and the kind of proof students love—because it’s real, and it turns “predator and prey” from a textbook phrase into something you can hold.

And when you stack 453 pellets worth of evidence together, you get something even better:

You get a pattern.

What the Data Is Really Saying

At a glance, this dataset is loud about one thing:

Barn owls are doing rodent control—constantly.

With voles (507), mice (329), and rats (223) leading the count, the “main course” is clearly small mammals.

That makes sense for barn owls, which often hunt open areas and edges where these prey animals travel—fields, fencelines, ditches, brushy margins, and anything that creates a safe “rodent highway.”

But the interesting part isn’t just what they ate.

It’s what those prey types suggest about the landscape.

Reading the Menu Like a Habitat Map

Voles: 507 — the grass-and-cover specialists

Voles tend to love dense ground cover—meadow grass, field edges, weedy strips, and places where they can move without feeling exposed. A high vole count usually points to habitat with lots of ground-level protection.

Translation for students:
If voles are common in pellets, there’s likely a lot of “soft cover habitat” nearby.

Mice: 329 — the flexible generalists

Mice show up in a wide range of environments—fields, edges, buildings, brush, and everything in between. They’re the “everywhere” prey.

Translation for students:
Mice in pellets often mean owls are hunting a patchwork: not one habitat, but many.

Rats: 223 — the human-edge connection

Rats can be associated with human structures and food sources, depending on species and location. Their presence can hint at hunting near barns, outbuildings, grain areas, or developed edges.

Translation for students:
Owls don’t avoid people-land. They often hunt the edges of it—because rodents are there.

Shrews: 121 — the tiny, high-energy insect-eaters

Shrews are small, fast, and insect-heavy in diet. Finding them in pellets can point to healthy ground-level ecosystems where invertebrates and leaf litter communities are doing their job.

Translation for students:
Shrews suggest the “understory engine” is alive—bugs, soil life, and the small predators that rely on them.

Moles: 95 — the underground specialists

Moles are built for tunneling. They’re not always easy prey, and their presence can hint at owls hunting near areas with active soil systems—lawns, fields, edges, and moist ground.

Translation for students:
Moles point to a thriving below-ground world—worms, insects, and soft soil habitats.

Birds: 128 — the surprise category

Students love this one because it breaks the “owls only eat rodents” assumption. Birds in pellets could represent opportunistic hunting, seasonal availability, or specific local conditions.

Translation for students:
Food webs aren’t rigid. Predators adapt to what’s available.

Insects & Other: 67 — the mystery drawer

This category is perfect for curiosity. Sometimes it’s insect remains. Sometimes it’s unusual prey fragments. Sometimes it’s the “we found it but it doesn’t fit neatly” pile.

Translation for students:
Real data isn’t always tidy—and that’s a feature, not a flaw.

Two Quick “Math Moments” Students Actually Enjoy

1) Prey-per-pellet thinking

This dataset has 453 pellets and over 1,400 prey items listed across categories. That naturally sparks the question:

“Do owls eat more than one prey animal per pellet?”
Often, yes—and the dataset is a perfect doorway into that concept.

2) Percent-of-diet graphing

Have students convert counts into percentages and make a bar chart. Suddenly you’re teaching:

• proportions
• data visualization
• interpretation vs assumption

…with bones. That’s a win.

Classroom Connection: “Pellet Data Detective Lab” (Graph + CER + Food Web)

Part A: Build the class graph

• Put the categories on the board: Voles, Mice, Rats, Birds, Shrews, Moles, Insects & Other
• Students build a bar graph from the counts.
• Add one sentence under the graph:
  “What prey category dominates, and what might that suggest about the habitat?”

Part B: CER (Claim–Evidence–Reasoning)

Claim: What type of habitat does this owl hunt near?
Evidence: Use at least 3 prey categories to support your claim.
Reasoning: Explain how each prey type connects to habitat features (cover, edges, human structures, underground soil systems).

Part C: Build the food web (the “connect everything” move)

Start with plants/seeds/insects → small mammals → barn owl.
Then ask: Where does snow, grass cover, and edge habitat fit into this web?

Teacher Tip

Have students label statements as Observation or Inference.

• Observation: “Voles were found 507 times.”
• Inference: “There are likely grassy edges nearby.”

This one habit upgrades every discussion that follows.

Product Pairing: Make the Outside Story Match the Inside Proof

This CU Denver dataset is built on one simple truth: pellets scale.
One pellet is a lesson. A class set becomes a dataset. A dataset becomes a habitat story.

To run this kind of learning in your own room:

• Owl Pellets → the evidence students can dissect, sort, and count
• Prey ID charts/posters → the bridge from “bones” to “species” (and from species to habitat)

The best part? Students don’t feel like they’re “doing an assignment.”

They feel like they’re doing what scientists do:
collect evidence → find patterns → make careful claims.

The Takeaway

This graphic isn’t just a set of numbers.

It’s proof that when students dissect, tally, and compare results, they’re not only learning owl biology—they’re learning how ecosystems reveal themselves.

Because a barn owl pellet is never just a pellet.

It’s a snapshot of the night shift.