This week NRT teachers will be visiting Easton 3rd graders to teach them about owls and what you can learn from their pellets! This is usually the part where a student will ask, “What’s an owl pellet?” Then another student will follow up with, “It’s what the owl poops out!” There ensues the explanation of owl digestive tracts and how owl pellets are actually regurgitated. Let’s explore…
When an owl consumes its prey, whether that be an insect, mouse, or another bird, it uses the sharp, hooked beak to tear and swallows pieces that then travel down the owl’s esophagus. Depending on the size of the prey, some owls will even swallow the prey item whole! Anyway, the food passes through the esophagus and into the first of a 2-part stomach. This first part is called the proventriculus. The job of the proventriculus is to begin the process of digestion by producing different digestive acids and enzymes. However, the stomach acid of owls is considered to be weak (pH 2.2 to 2.5), so that only the soft tissues of the prey will break down. The food will then move to the second part of the stomach called the gizzard, which acts like a strainer. The digested soft tissues will move through the gizzard into the intestines to be absorbed and used for energy, while the undigested bones and fur will remain in the gizzard.
So far, so good? Because things are about to get interesting! Think of the gizzard like a trash compactor, using muscles to continuously compact indigestible parts into these solid, oval pellets. The compacted pellets will remain in the gizzard until the owl is ready to eat again, and because the pellet prevents the owl from eating, there is only one way to get rid of it so that the owl can feast. The esophagus will start spasming causing the pellet to be pushed up the esophagus and out through the mouth. Viola! You now have a regurgitated owl pellet!!!
So what can we learn from owl pellets? We can get a good picture of what an owl’s diet is and what prey species are available in the environment. We can learn if there are any seasonal changes in diet. We can reconstruct skeletons of the recovered bones of the prey. Overall though, we get an excellent picture of an owl’s role in the food web and how important owls are for the continuing success of all animals within an owl’s habitat!