What is an Owl Pellet? - Facts, Dissection & Lab

Instructor: Taormina Lepore

Taormina has taught advanced high school biology, is a science museum educator, and has a Master's degree in museum paleontology.

An owl pellet can tell us a great deal about the diet and digestion of an owl and the structure of owl prey. In this lesson, we'll cover all the basic owl pellet facts and conduct a dissection lab with step-by-step instructions.

What Is An Owl Pellet?

Think about the last bird you've seen and visualize the inner structure of its beak. What do you notice?

Modern birds don't have teeth!

Many birds have evolved mechanisms to help them break down and digest their food without that first, basic step that we as humans sometimes take for granted. Chewing, also known as mastication, is the mechanical breakdown of food. Birds simply cannot chew.

The crop is a modified sac that holds food and aids in digestion. Owls lack a crop.
Crop organ in a pigeon

Since birds can't chew, many possess a specialized organ called a crop, which holds food for later consumption. From the crop, food then passes to the muscular stomach, or gizzard, for chemical digestion. There, the food is chemically broken down before being expelled. Other birds of prey also have a crop, which allows tough material to be turned into a slurry mass.

But owls don't have a crop, and so food passes directly from the mouth to a temporary digestive organ called the proventriculus. From the proventriculus, the food then passes to the gizzard, or ventriculus.

Digestive system of an owl
Owl Digestive System

The digested meal will pass from the muscular stomach, or gizzard, to the small and large intestine, where nutrients are absorbed and the waste is excreted. Most of us are familiar with the white, liquid consistency of bird droppings. Much of this liquid is actually urea, an acid that is essentially a combination of urine and fecal waste. This waste then passes through the owl's combination reproductive and excretory opening, the cloaca, and out of the body.

What about those bones, fur, scales or feathers? These are harder to digest and, without teeth or a crop to help further digestion and store the food, owls just can't break down these tougher materials. The undigested food remains in the gizzard, blocking digestion for about ten hours.

So they do something that's both fascinating and a little disgusting.

They throw up, or regurgitate, the undigested fur and bones in a compact oval known as an owl pellet.

These owl pellets have been freshly regurgitated.
Regurgitated owl pellets

Owl pellets are one of the coolest things we can dissect and observe. Biologists use owl pellets to look at prey anatomy and the digestive health of owls. When an owl regurgitates an owl pellet, that's a good sign that the owl is ready to eat again.

Can you think of a question you might want to answer using the contents of an owl pellet?

Let's delve deeper into the topic and create your own question in our lab.

Owl Pellet Dissection and Inquiry-Based Lab

The purpose of this lab will be to dissect and analyze the contents of an owl pellet. You can begin by creating sections in a notebook with each of the below headers, starting with a title for your lab, then the materials, questions and hypothesis, procedure, and so forth.

You'll also need to obtain owl pellets. There are a number of sources to order pellets and supporting materials by mail. Here are just a few:

http://www.pelletsinc.com

http://www.carolina.com/owl-pellets/owl-pellets/FAM_227880.pr

http://www.owlpelletkits.com/

Materials

  • Owl pellets
  • Two (2) pairs of tweezers
  • Paper towels
  • A guide to prey animal skeletal anatomy
  • A magnifying glass (optional)

Question and hypothesis

Before you begin your lab, think of a question you'd like to answer. Write down your question in your notebook.

Once you've come up with a question, think about a hypothesis that will answer the question.

Let's say we choose as our question, 'What can owl pellets tell us about owl digestion speed?' In this case our hypothesis could be, 'I think that if owl pellets contain bones with very little damage, then the speed of owl digestion of bones is slow.' Notice how the hypothesis has an 'if...then' phrasing. That's one way in which we can build a hypothesis to answer our question.

Procedure

Begin by spreading the owl pellets out on a piece of paper towel to keep your work area clean. Then, using the tweezers and a magnifying glass (optional), you can pick apart and inspect the pellets. You will find that the pellets pull apart fairly easily with the use of the tweezers.

What do you find inside the pellets? Describe what you find, draw what the pieces look like, and record their condition. Think about how your descriptions can help you answer your question.

Record your results

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