Researching
Regurgitation
By Colin Hascup
Period 1 (13)
Introduction
Comparative Question
We dissected owl pellets to find out what the barn owls ate. My comparative question was
“Where do owls eat the most prey?” My hypothesis was that owls in the northeast would
have the most skulls. My hypothesis was disproven.
The barn owls in the northeast had an average of 3.45 skulls in each pellet. The barn owls in
the northwest had an average of 2.23 skulls in each pellet. The barn owls in the southeast had
an average of 2.53 skulls in each pellet. The barn owls in the southwest had an average of
3.65 skulls in each pellet. I found these numbers interesting. The southwest had the most
skulls. I think this is because the population of the prey animals is higher in the southwest
than any other region of the United States.
I had predicted that the pellet from owls in the northeast would have the most skulls. This is
because I had 4 skulls in my pellet and some people in my class had up to 8 skulls. But I
didn’t account for the other pellets in my class. In science, we need to use multiple samples.
Procedure
First we picked our owl pellets, then we weighed and measured
each pellet. We labeled the length, width and height of each pellet.
Next we dissected our pellets. We looked for bones using a
toothpick and tweezers to pry apart the thick fur. We found as many
bones as we could. When we were done dissecting, we identified
the bones and put them in specific categories according to body
part. Then we counted up the parts to determine how many full
animals were in the pellet. We recorded how many animals we had
and glued one of the sets of animal bones to a bone chart and
labeled it.
Bone Chart
Owl Questions
Graph of the types of prey animals
found in pellets.
Graph of the number of prey
animals found in pellets.
Graph of the average number of
skulls in barn owl pellets.
Source:
California Owl
Pellet App
Graph of the number of bones
found in my pellet.
Size of owl pellet chart
Charts of prey animals found in pellet
Vole
3
Mouse
1
Conclusion
Barn owls have adapted to become amazing birds of prey. The dissection of owl pellets was
used to figure out what owls eat. A complete skeleton of a vole was constructed with the bones
from the owl pellet.
In addition, extra research was conducted to evaluate “Where do owls eat the most prey in the
United States?” For this research the California Owl Pellet App was used. The hypothesis that
owls in the northeast region of the United States would have the most skulls was refuted. Owl
pellets had the most skulls in the southwest, possibly because there are more prey animals in the
southwest. However, only one source was used to obtain the average numbers of skulls in the
pellets. These numbers could have had a possible source of error. There is human error from
counting wrong or mis-identifying the skulls. Another possible source of error is that pellets from
other owl species could have been included. A way to improve this lab would be to use multiple
sources for finding the data.
Owl pellets are a very useful scientific tool to help scientists determine what owls eat. In addition,
apps like the California Owl Pellet App have pros and cons. They are useful because many
people can report data. This is good because it gets a lot of samples, but bad because it might
introduce a lot of error.
Fun Facts!!!
1. Barn owls screech, they do not hoot.
2. The barn owl’s heart-shaped face collects sound in the same
way as human ears.
3. Its hearing is the best of any creature tested.
4. Owl chicks in the same nest will feed each other.
5. In order to live and breed, a pair of barn owls needs to eat
around 5,000 prey items a year.
6. The barn owl is found on every continent except Antarctica.
7. Nests are usually in barns or holes in trees, but sometimes they
build their nests in quarries