Name _________________________________ Class ___________ Date _____________________
Unit 1
Interactions and Ecosystems
Performance Based Assessment - Owl Pellet Lab
Knowledge Outcome:
Students will trace and interpret the flow of energy and
materials within an ecosystem.
 analyze ecosystems to identify producers,
consumers and decomposers; and describe how
energy is supplied to and flows through a food
web
Skill Outcome:
Students will conduct investigations into the relationship
between and among observations and gather and record
qualitative and quantitative data.
 use research information to help in solving a given
problem
 compile and display data
 use a classification chart
Attitude Outcome:
Students will work collaboratively in carrying out investigations
and in generating and evaluating ideas.
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Owl Pellet Lab
“Hoo is Eating Who?”
Pre-Lab Discussion (Background Information):
Owl pellets, and the pellets of other raptors (meat-eating birds of prey) can be very useful tool for
field biologists or students of field biology.
Owl pellets are masses of bones, hair, teeth, feathers and other indigestible parts. These pellets are
produced in the stomach of many owls, eagles, hawks and other birds of prey. When a raptor
swallows its prey whole, the soft parts are digested by enzymes in the stomach. Any parts that are
not digested cannot fit through the tiny intestine and must be regurgitated. The stomach forms all the
fur, bones and other hard parts into a slimy pellet – nearly all the bones end up in here. One pellet
usually has one or more complete skeletons in it, which may be examined to determine the diet of the
bird.
In this lab, you will be dissecting pellets from a barn owl. These owls eat in the early evening and then
regurgitate one pellet about 20 hours after eating. Therefore, one pellet shows the diet for one day
of the owl’s life. By examining the bones of the animals eaten, the types of animals eaten, and the
number of each species, the varied diet of an owl and the type of ecosystem in which it came from
can be determined.
You will examine the bones found in the pellet to identify what animals the owl ate. The most common
prey for barn owls include smaller birds, mice, moles, voles, shrews, rats and insects. The easiest
part of the skeleton to identify is the skull.
Name _________________________________ Class ___________ Date _____________________
Owl Pellet Lab - “Hoo is Eating Who?”
Carefully read and fully understand each part of the investigation before beginning the lab.
Problem:
Looking at an animal’s scat (feces) or what an animal has in its stomach is one way to find out what
niche it occupies.
How can a barn owl’s niche be determined by examining the contents of its pellet?
Hypothesis:
Materials:
Owl pellet, magnifying glass, dissecting tools (toothpicks/tweezers/probes), bone chart, paper, plastic
baggie, coloured paper, glue or clear tape
Safety:
The owl pellet you will dissect has been dried and sterilized. It does not contain any harmful or
disease carrying organisms. After the investigation, take the time and care to wash your hands
properly.
Procedure:
1.
2.
3.
4.
5.
6.
7.
8.
9.
You will be working in a group of two.
Prepare a clean working area on your desk.
Obtain 1 owl pellet per group, toothpicks/probes/tweezers and plastic baggie.
Label the baggie with your names.
Open the aluminum foil carefully.
Examine the outer surface of the owl pellet.
Measure the length, width and estimate the weight of your pellet. Record this data on Table 1.
Carefully examine the exterior of the pellet. Record your observations in Table 1.
Carefully use a toothpick or other dissecting tools to break apart the owl pellet and observe
what is within the pellet. Expose all the bones for identification. Use a bone diagram to help
you identify your bones and complete the chart. Record your information in Table 2.
10. Create a chart on construction paper to mount the bones you find. Organize them by the type
and by the animal. (You can challenge yourself by re-constructing the organism that you have
found.)
11. If you do not finish and need to continue the next day, place your pellet and bones into the
plastic baggie for later. Return the tools.
Name _________________________________ Class ___________ Date _____________________
12. Near the end of the period, make sure that your area is clean and free of pellet and bones.
Properly dispose of any remains that you are not using for identification. KEEP THE BONES
FOR MOUNTING.
13. The bones can be mounted on construction paper with regular glue.
14. Answer the analysis and conclusion questions when you are finished cleaning your work area
and mounting the bones.
15. Your mounts will be graded on neatness, organization and proper identification.
Observations:
Table 1
Length of the owl pellet
__________ cm
Width of the owl pellet
__________ cm
Estimated mass of the owl pellet
Hint:
a pencil has a mass of about 50 g
__________ grams
Exterior Observations of the Owl Pellet
Do you see any signs of fur/feathers? Describe the texture of the owl pellet?
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Table 2
Bone
Skull
Jaw
Scapula (shoulder)
Forelimb
Hindlimb
Pelvic Bone
Rib
Vertebrae (Back Bone)
Type of Animal (List All)
Number Found
Name _________________________________ Class ___________ Date _____________________
Analysis and Conclusion:
Use the bone chart to identify the bones found in the owl pellet. After the bones have been mounted
and labelled on the piece of construction paper, complete the analysis and conclusion.
This part of the Performance Based Assessment must be completed individually. Read each
question carefully. Answer questions in detailed, well-thought out sentences. Use part of the question
on your answers.
1. How are owl pellets made?
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2. What do we know about the digestive system of an owl based upon the pellets?
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3. How is an organism’s niche determined?
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4. In what type of ecosystem did your owl hunt? How do you know? (In other words, describe the
barn owl’s niche.)
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5. If all the owls whose pellets your class studies lived in the same ecosystem, what
generalization could you make about the population size of the most common prey?
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6. In your own words, describe the meaning of ecosystem.
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Name _________________________________ Class ___________ Date _____________________
7. Why could an owl pellet be considered a little ecosystem on its own?
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8. A food web is a relationship diagram showing organisms arranged by energy flow from
organisms at lower levels to higher feeding levels. A food web is a series of food chains
connected at various points.
Within an ecosystem, energy passes from one organism to another on a higher level through
the consumption of a lower organism. This pathway of energy is how nutrients pass through an
ecosystem.
Show your understanding of energy transfer by neatly constructing a food web (of at least 5
animals) with an owl at the uppermost level. Use arrows to show which organisms are in the
three trophic levels in the food web – primary consumers, secondary consumers and
tertiary consumers.