Name ____________________________________________________ Date ________________________________ Period _____
Owl Pellet Dissection
Introduction
Barnyard Owl
The barn owl is a nocturnal bird that lives in many different habitats including cliffs, grasslands and old buildings.
Barn owls are predators that hunt many different small mammals including mice, rats, birds, voles, shrews and
insects. During the day, barn owls sleep in their nests located in trees, on the sides of mountains and in buildings
around farms.
Owl Pellets
In lab, we will dissect an owl pellet to determine what the owl has recently eaten. Owl pellets are NOT the same as
owl “poop.” Owls vomit these pellets out of their mouths.
Owl pellets are masses of bone, teeth, hair, feathers, and more! Owls feed early in the evening and spit up a single
pellet about 12-20 hours after eating. Unlike snakes, the enzymes and strong acids of owls do not digest the entire
meal. The weak stomach muscles of the bird turn the fur, bones, feathers, teeth, and hair into wet slimy pellets.
In the Lab
We will identify the bones found in the owl pellet. We will use the bones to make a food web that includes the
predator and its prey. We will label the producers and consumers in the food web, as well as the trophic levels. We
will analyze an energy pyramid that shows how much energy is found at each level of the food web, as well as a
pyramid of numbers which shows how many organisms are found at each level of the food web.
Questions. Answer in full sentences.
Section I. The Barnyard Owl
1. Where do barnyard owls live?
2. What do barnyard owls eat?
3. What is the role of the barnyard owl in the food chain? In other words, what level of consumer do you think it is?
How do you know?
Section II. Owl Pellets
4. What is an owl pellet?
Section III. In the Lab
5. What is the purpose of our lab today?
6. What is an ecological pyramid?
Materials and Methods
Materials: Owl pellet, ruler, sheets of white paper, tweezers and toothpicks, a bone identification key and a skull
identification key
Methods:
1. Make measurements and observations of the pellet
2. Carefully dissect the pellet and remove the bones.
4. Go through and identify each skull using the key. Fill in Table 1.
3. Go through and identify each bone using the key. Fill in Table 2
5. As a whole class, we will share our Table 2 data and make a bar graph of the entire class’ data.
*Safety note: After the lab, you must clean my hands thoroughly with hand sanitizer and/or soap and water! ____
Results
Part I. Outside the Pellet
Pellet length: ______ centimeters
Pellet width: ______ centimeters
Pellet observations: Describe the outside of your pellet in two or more full sentences. (What does the outside of the
pellet look like? Do you see fur, feathers, seeds, grains, dirt, or hay, or pine needles stuck to it?)
Part II. Bones Found Inside the Pellet
Table I. Different Skull Types
Using the skull identification keys, identify the skulls found in your pellet.
Animal
Tally the number of skulls
Mouse
Vole
Rat
Shrew
Mole
Bird
Table II. Different Bone Types
Using the identification keys, tally the different types of bones you found
in your pellet.
Bone Type
Tally the number of pieces
Skulls
Ribs
Jaws
Pelvis (hips)
Scapula (shoulder blade)
Limb bones (legs)
Vertebrae (pieces of spine)
Other
Summary of results: Which type of
animal was most common in your
pellet?
Summary of results: Which type of
bone was most common? Which
one was least common? Why do
you think this is?
Figure 1. Bar graph of the whole class’ results
Summary of results: Out of the
entire class’ owl pellets, which
animals were the most common?
Which ones were least common?
Conclusion Questions
If a question has a star (*) please answer in complete sentence.
Part III. Food webs
1. What did the barnyard owls that made the class’ pellets eat? Using the class’ results, make a food web with
the barnyard owl and its prey. Include 5 total organisms. Label the producers and the primary, secondary,
and tertiary consumers for one chain in the web (Use Section 3, page __ if needed). Also label the carnivores,
omnivores, and herbivores. Each organism should have two labels!
2. What level of consumer is the barnyard owl in the food web that you’ve drawn? How do you know?*
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Part III. Trophic Levels and Making Pyramids
The amount of energy or number of organisms in an ecosystem can be
illustrated by drawing ecological pyramids.
3. Based on your food web, fill in the following with one example
4th trophic level= tertiary consumer= Owl
__rd trophic level= _____________ consumer = _________
__nd trophic level= _______________________= _________
__st trophic level= ________________________= _________
4. Now, turn your food web into a pyramid!
Part IV. Energy Pyramids and the Pyramid of Numbers
An energy pyramid is a pyramid that shows how much energy is in each trophic level. According to the Rule of 10,
only about 10% of the energy in one trophic level is moved up to organisms at the next trophic level.
5. What are some activities that the owl’s prey does that uses up its energy? ___________________________
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6. What are some activities that a producer does that use up its energy? _______________________________
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7. Why doesn’t ALL the energy of an organism pass up to the next trophic level? In other words, how come the
consumer that eats an organism only gets 10% of its energy? *__________________________________
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Compare the energy pyramid on the left to the pyramid of numbers on the right. The pyramid of numbers shows the
number of each organism in the ecosystem.
Figure 1. Energy Pyramid (kcals measure energy)
Figure 2. Pyramid of numbers
8. The pyramid-like shape of the energy pyramid shows less ___________ as you go up the trophic levels.
9. The pyramid-like shape of the pyramid of numbers shows that there are usually fewer ______________ as you
go up the trophic levels.
10. In your own words, what is the difference between the two types of pyramids? _______________________
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11. Why are there fewer animals as you go up the trophic levels? (Hint: Think about what animals need to
survive!)* _____________________________________________________________________________________
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Part V. Critical Thinking
12. Other types of birds form pellets. What might you find in the pellet of a seagull? _____________________
13. Based on the evidence available in your results (the outside of the pellet and the type of prey found), create a
2 sentence description of the area the owl was hunting that day.* ___________________________
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