Students will be able to:
- analyze and interpret data they have collected from an owl pellet dissection to answer a question.
- use a dichotomous key to identify bones of prey species found in an owl pellet.
Image credit: Charles Welch
What animals did your barn owl eat this week? Observe the bones it swallowed to identify its prey!
Students will be able to:
Optional materials to create a miniature collections tray for one's findings:
Part 1: I notice, I wonder…
NGSS Connection: This portion of the lesson connects to the Practice of Asking Questions because students generate their own questions about owl pellets through firsthand observations using the “I notice, I wonder” sentence starters. Questions that are generated from student’s firsthand observations help them to develop their own ideas and explanations for phenomena in the natural world. Students’ questions can be recorded on the Owl Pellets Dissection worksheet. Students can also select one of their questions to try and answer with throughout the course of their dissection.
Educator Tip: Be sure to address the misconception that owl pellets are poop. Owl pellets are regurgitated material that cannot be digested.
Part 2: Dissection
Educator Tip: Student’s excitement over the first bones that are uncovered can lead to distraction from the dissection. Encourage students to stay organized, follow the procedure, and keep careful track of what they find.
Educator Tip: During the time that students are dissecting their owl pellets, you can draw the class data table and “Percentage of Prey Species Found in Owl Pellets” graph from the What do owls eat? worksheet on the board.
Part 3: Dichotomous key
NGSS Connection: This portion of the lesson connects to the Practice of Analyzing and Interpreting Data because students must draw conclusions from their analysis of the data table and bar graph to determine which of the prey species was eaten the most by the owls. Based on their calculations of fractions and percentages, students should be able to determine the answer to the scientific question, “Which prey species was eaten the most by the owls?”
NGSS Connection: This portion of the lesson connects to the Crosscutting Concept of Patterns because students are asked to identify patterns in the data to make a prediction about the owl’s environment. For example, if your class data shows that 90% of the prey species found in the owl pellets were voles, then you can predict that voles were the most abundant prey species in the environment.
Part 4: Display owl pellet bones in a petri dish (optional)
Discuss with the students:
NGSS Connection: This portion of the lesson connects to the Crosscutting Concept of Structure and Function because students are asked to observe the shape and size of the prey species’ teeth and think about how that is related to their function. For instance, the skulls of rodents, such as mice and voles, have front teeth that grow continuously. These front teeth help them to nibble the leafy vegetation that they eat. Moles and shrews will have differently shaped teeth because they have a different diet.
1. Candy is chocolate. Go to 2.
Candy is not chocolate. Go to 3.
2. Candy is rectangle-shaped. Hershey’s bar.
Candy is circular-shaped Go to 4.
Owls swallow their prey whole, therefore in addition to the meat that they digest for food, they swallow other material such as bones, fur, or feathers. Owls are unable to digest these materials, so they are regurgitated in a compacted mass. This compacted mass of fur, bones, and any other indigestible material is called an owl pellet. Despite what it looks like, pellets are not owl poop (which is what many students assume). Owl pellets are more like owl puke.
Most owls produce about two pellets each day. A pile of pellets can often be found below an owl’s roosting site. The bones of prey that are found within an owl pellet can be identified with the help of a dichotomous keys or bone-sorting charts. Studies with captive owls have shown that pellets give an almost perfect record of what the bird has actually eaten. The contents of owl pellets provide a fascinating window into the life of a barn owl. In fact, fossilized pellets have been used to study the diet of ancient owls.
The pellets provided with this kit are collected from common barn owls (Tyto alba). Barn owls are the most widespread species of owl and one of the most widely distributed vertebrate species on the planet. They are found on every continent except for Antarctica.
Barn owls hunt in open areas, such as fields, marshes, and grasslands. They are mainly nocturnal and depend on their remarkable sense of hearing to hunt. Their hearing is so accurate that they are able to capture prey in complete darkness. Barn owls nest in enclosed spaces, such as small caves or holes in trees. Human-built structures, including barns, also provide comfortable nesting spaces. Human activities, such as clearing forests for farmland, have extended the open areas in which barn owls can hunt.
Barn Owl prey species
While some predators prefer to eat a specific type of prey, others are less picky and will eat whatever is readily available. Barn owls eat a mixed diet of whatever small critters they can catch in their fields. They feed mainly on the small land mammals that live the fields where they hunt. They will also eat small birds, bats, and occasionally small reptiles. As a result, the barn owl diet varies regionally depending on what prey animals are common in the area. For example, owl pellets from Northwestern United States most frequently contain the remains of voles, which are abundant in the area. On the other hand, voles are absent from parts of the Southeast; in those areas, rats are more commonly found in owl pellets.
The pellets provided with this kit are collected in the Pacific Northwest and Northern California. Common prey of barn owls in this region include the following:
Rodents are mammals that have front teeth that grow continuously. 40% of all mammal species are rodents.
These animals are not rodents because they lack the characteristic of continuously growing incisors. Moles and shrews belong to a group of mammals called insectivores. Bats belong to their own group and are the only mammals capable of true flight. Other mammals commonly eaten by barn owls include:
While mammals are the consistent staple of a barn owl’s diet, small birds are an important alternative during the winter, when mammals tend to be less active and more difficult to find. Bird bones are thin and delicate; as a result they may be partially digested by barn owls, making them more difficult to find in the pellets.
Science and Engineering Practices
K-2: Ask questions based on observations to find more information about the natural and/or designed world(s). Ask and/or identify questions that can be answered by an investigation.
3-5: Ask questions that can be investigated and predict reasonable outcomes based on patterns such as cause and effect relationships.
Analyzing and interpreting data
K-2: Use observations (firsthand or from media) to describe patterns and/or relationships in the natural and designed world(s) in order to answer scientific questions and solve problems.
3-5: Represent data in tables and/or various graphical displays (bar graphs, pictographs and/or pie charts) to reveal patterns that indicate relationships. Analyze and interpret data to make sense of phenomena, using logical reasoning, mathematics, and/or computation. Compare and contrast data collected by different groups in order to discuss similarities and differences in their findings.
6-8: Construct, analyze, and/or interpret graphical displays of data and/or large data sets to identify linear and nonlinear relationships. Analyze and interpret data to provide evidence for phenomena.
Disciplinary Core Ideas
K-LS1-C: Organization for Matter and Energy Flow in Organisms
4-LS1-A: Structure and function
K-2: Children recognize that patterns in the natural and human designed world can be observed, used to describe phenomena, and used as evidence.
3-5: Students use patterns to make predictions.
6-8: Students use patterns to identify cause and effect relationships, and use graphs and charts to identify patterns in data.
Structure and function
K-2: Students observe the shape and stability of structures of natural and designed objects are related to their function(s).
3-5: Students learn different materials have different substructures, which can sometimes be observed; and substructures have shapes and parts that serve functions.
Related Performance Expectations
Remember, performance expectations are not a set of instructional or assessment tasks. They are statements of what students should be able to do after instruction. This activity or unit is just one of many that could help prepare your students to perform the following hypothetical tasks that demonstrate their understanding:
MS-LS2-2: Construct an explanation that predicts patterns of interactions among organisms across multiple ecosystems.
Martin, Jason M., Richard N. Raid, and Lyn C. Branch. (2005) Barn Owl (Tyto alba). Retrieved September 25, 2008 from University of Florida IFAS Extension website: http://edis.ifas.ufl.edu/UW216
Sparks, John and Tony Soper. (1970) Owls: Their natural and unnatural history. New York: Taplinger Publishing Company.
Taylor, Iain. Barn owls: Predator-prey relationships and conservation. Cambridge: Cambridge University Press.
Tyler, Hamilton and Don Philips. (1978) Owls by day and night. Happy Camp, CA: Naturegraph.