Whoo Wants Leftovers?

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Objective

SWBAT describe what and how an owl pellet is formed. SWBAT dissect an owl pellet and identify its contents to hypothesize about the predator's habitat and food sources.

Big Idea

By examining owl pellets, we are able to map the whereabouts of certain species, identify predator-prey relationships, and learn about the ecosystems that are suitable for owls to live and thrive.

Prior to Teaching

5 minutes

This lab involves the dissection and examination of owl pellets. Students will need the materials below in order to complete the lab. While many are common household or classroom items, some will need to be pre-ordered prior to beginning this activity.

  • Owl pellets* (one for demonstration purposes and one for every 1-2 students)
  • Black construction paper
  • Magnifying glass, toothpicks, rulers, tweezers, and/or other examination tools
  • Small spray bottle (for water)
  • Lab aprons and latex gloves* (optional)
  • Owl Pellet Bone Chart, to identify skeletons of prey. It can be downloaded for free from the Carolina Biological Supply Company (scroll down to the bottom of their page)
  • Graph paper and markers or colored pencils

*Owl pellets contain regurgitated bones, fur, and feathers that owls cannot digest. Pellets can be ordered from a scientific or biological supply company. Commercial pellets are recommended over pellets found in nature, as they have been sterilized and can be handled safely with bare hands.

Engage

10 minutes

I always like to provide a "hook" to ignite students' curiosity and set the stage for active engagement at the beginning of every lesson. With 6th graders, I find that two things tend to to this very well - multimedia and grossness. Middle-schoolers will almost always choose to be anywhere except for school, but no 12-year-old can deny that a listening to a catchy song, viewing an interesting video, or handling something slightly mysterious and absolutely gross are an awesome way to start a class!

To get students interested in this lesson, I combine a little of everything. I start by passing around the largest owl pellet I can find, and having my students guess what it might be by writing their ideas on a sticky note. Kids who have worked with pellets will easily figure it out, but many will have no clue. I collect the sticky notes and read some of them aloud to the class. I try not to read the correct ones, because I don't want to give it away just yet. I pose the following question:

"What if I told you that you just handled animal vomit?" (Wait for reaction...) "Well, this isn't exactly animal vomit, but it is close!"

Next, I play the Northern Saw-whet Owl video. The first time I viewed it, I thought about muting the audio when I showed it in class, as the people filming the owls are having a side conversation. But once the owl coughs up a pellet, their reaction is priceless, so I decided to keep the audio on.

Another option for a great introduction video (no sound, but the picture quality is great and you can watch at two different speeds).

 

By this time, I have definitely gotten everyone's attention! Not only are they dying to know what this really is, but they're also curious as how it happens. This means they are ready to learn!

Explore

60 minutes

I have the students pair up and pass out the Owl Pellet Cloze Activity. Working in pairs, the students will read through the page, filling in the blanks with terms they feel make the best sense. This will provide some background information, while still requiring students to read closely and use their best judgement to help them make sense of a scientific process. It will also provide focus for the lesson.

Next, the same groups of students will read through the "Pellet Information" pages of the Kidwings website related to owl pellet dissection, completing the cloze activity as they read. While working on the activity, I also have the students highlight any new and/or unfamiliar words they come across as they read.After filling in the entire paper, I have them define the words they highlighted (including, but not limited to regurgitate, proventriculus, and gizzard) in the margins next to the first place where they are mentioned. This will provide vocabulary support to students as we discuss the cloze activity and as they complete the lab.

After the activity has been completed by everyone, we discuss the answers and I ask clarifying questions to gauge understanding and extend thinking, such as:

  • Why is it necessary for the owl to do this? What would happen if they did not regurgitate these pellets?
  • Humans do not have a proventriculus. What organ do they have instead?
  • Why don't all birds produce pellets?
  • Which birds in our ecosystem might produce pellets? What you might see in the pellets of these birds? 
  • So is this really the same as vomit? Why or why not?

 

Once we have discussed the process and I am sure the students understand the concept and processes involved, we move on to the lab. I begin by modeling the owl pellet dissection while students observe. Keep in mind, the purpose of the demonstration is for students to understand the process, not for the teacher to give away the discoveries!

Step 1: Put pellet on black construction paper.

Step 2: Observe outside of pellet before opening it. Measure it.

Step 3: Ask students for their predictions about what’s inside.

Step 4: Show how to use a lab report sheet.

Step 5: Pretend to do lab, answering student questions about the process.

Once all questions have been answered, I asked a few rapid fire questions about the process to make sure everyone was paying attention and knows how to perform the dissection. Then it is time for the students to participate. I help students create groups of 4 and select roles for the lab. Then I have each Materials Manager collect black construction paper, a wrapped pellet, toothpicks, rulers, aprons, gloves, Lab Guides for each participant, and an Owl Pellet Bone Chart for each table. 

Once each group has their materials, they begin the lab, using one of the guides below, both found on the Scholastic website. I prefer Guide II, as it is a little more challenging, but I always offer Guide I to my ELL and Special Ed students, as well as anyone else who requires a task that is easier to follow, based on the vocabulary, word count, and number of tasks. I circulate the room, encouraging participation and inquiry, and observing student progress. I also spray the pellets with water if requested, as it makes them easier to pull apart. (Warning: it also makes them smellier!)

After approximately 30-40 minutes, I have students stop their work and assist the Materials Manager in cleaning up and returning the materials to the proper place. They also place their pellet remnants in a Ziploc baggie and label it with their names, I keep them so they can be used for another activity the next day (see "Elaborate" section.) We discuss the process and discoveries they made as they dissected.

Scholastic Lab Guide I (beginner)

Scholastic Lab Guide II (intermediate)

Explain

30 minutes

Now it is time to record and analyze our findings. I explin to the students that we will take a lok at the many items each group found in their pellets. I have the students take out their lab sheets. One at a time, groups share what they found in their pellets, including the quantity of each. I record these results on the board, using a table.* Once we have collected everyone's data, the students will make a graph of their findings to add to their science journals. This will provide a visual interpretation of the class results, which is easier for many to read and analyze.

Next, I ask students for statements they could make based on data:

  • What do we know about what owls eat?
  • Were our predictions accurate? (Refer to predictions on Lab Guide I.)
  • Was there anything in our data that surprised you?
  • Why do you think we got the results we did?
  • What factors could make a significant change in our data?

 

*How you choose to sort this data is really up to you. Sometimes, I keep it very general, labeling and counting the number of bones, fur, rocks, etc. Other times, if we have found more variance in our findings or if the students have more of an interest or a background in anatomy, we will classify by the type of bones (skull, jaw, femur, etc.) How you choose to sort your findings will not affect the lesson, but may result in a larger graph, and therefore more time creating it, but it also provides for richer discussions afterwards.

Elaborate

30 minutes

After analyzing the data, I pass out the bags that contain the pellet remains and allow the students use the Owl Pellet Bone Chart to piece together skeletons and glue them to cardboard with craft glue. Many will ask to "trade" bones with other groups in order to get a complete skeleton, which I always allow. Others will use what they have to make the closest resemblance to a skeleton that they possibly can. Be prepared for creative skeletons!

Evaluate

5 minutes

I tend to assess students based on observation and anecdotal notes that I take throughout the lesson. Here’s what I’m looking for. Did students:

  • participate in the lab (virtual or hands-on)?
  • organize themselves and their materials?
  • ask questions?
  • stay on-task?
  • help one another?
  • gather and record data accurately?
  • draw conclusions and interpret data?
  • construct an anatomically correct skeleton?

If time permits, I also have the students select two of the following questions and respond by writing a short paragraph for each. Not only can I use this to assess their understanding, but I can also use this as a way to assess their ability to respond in writing to an expository writing prompt.

1. What do we know about the habitat, the niche/s, and the digestive system of an owl, based upon the pellets?

2. Owls, hawks, and eagles are types of raptors, animals which have hooked beaks and sharp claws, and are therefore adapted for seizing prey animals. Hawks and eagles differ from owls in that they eat their prey animals by tearing them into small pieces, picking out the flesh and avoiding most of the fur and bones. They also have strong stomachs which can digest most of the bone material which they might eat. The relatively small amount of indigestible bone and fur that remain will be compacted by their stomach muscles into a pellet similar to the owl's. Do you think an eagle pellet would be as useful for dissecting as an owl's? Why or why not?

3. Construct a diagram of a food web (of at least 7 species) with an owl at the uppermost level. Write a narrative that explains the food web in the context of the ecosystem in which it resides.