Students are presented with the real world problem, how the size and design of a bird house makes a difference in which birds can successfully use it. One of my favorite birds is the bluebird, whose numbers are declining because of the loss of their habitat from forest fires, logging, and developing new areas for homes. Also, other birds are more aggressive and take over the natural nesting sites of bluebirds. One way to help bluebirds is to create nest boxes, commonly known as bird houses, for the bluebirds.
There are important requirements in creating a proper nest box for a bluebird. If the nest box is too large or too small, other birds will take over the nest box. Also, predators of bluebirds will be able to get inside the nest box and harm the eggs or birds. Nest boxes need to have a proper size opening for the bird, air vents, and shade.
The proper size of a nest box is determined by area, which should be somewhere between 625 to 750 square centimeters. Helping the students make the connection from the real world setting to the math required for Common Core, I ask the students,
"What math will you need to know to make a nest box?"
"What math do you already know that will help you to make a nest box?"
"What do you think of with the term nest box?"
"What else would be required for a bird to survive inside of a nest box?"
I explain the objective of this math unit will be to design your own nest box for a bluebird with an area that is at least 625 square centimeters and less than 750 square centimeters. The base of the nest box needs to be 180 square centimeters, and this is the smallest area on the nest box.
To review some of the area skills the students will be using in this lesson, I have the students draw an L shaped polygon on their whiteboards. I assign measurements to each side, and the students will find the area of this polygon.
Students create a plan, working with a partner, to build a nest box using centimeter grid paper. The partners work together to determine the area of each side of the box.
I decided that a partnership model will make the actual construction of the nest box more accessible for all of my students. I chose to group my students heterogeneously so that each pair can be successful and create a box. This will also give students the opportunity to teach and learn from each other. As partners, students have the extra hands to support pieces during the assembly of a prototype.
Students create their plan based on the dimensions of the floor of the nest box, which is a given 180 square centimeters. I provide centimeter grid paper with the expectation that my students use their knowledge of the distributive property of multiplication to solve to find a rectangle with an area of 180 square centimeters. One of the four critical areas for 3rd grade students is that they connect area to multiplication, and justify using multiplication to determine the area of a rectangle.
Students can demonstrate this property with (12 x 10) + (12 x 5) = 180, or any other combinations to equal 180. I chose this measurement because it allows for an appropriate size for the bird, and it also is a number with the most factors. Using the base measurements the students will determine the sizes and area of the sides and the roof to complete the nest box.
As students work, they need to subtract the base measurement from the total surface area to determine the remaining area for the other sides and roof of the box. Also included will be addition sentences to show the total surface area of the nest box including the base, roof, and four sides.
I chose to use centimeters as the unit measurement, because it is the unit used in the Common Core Standards for third grade, and because it allows students to use the distributive property to solve equations such as 12 x 15 = 180.
I remind the students of some of our prior research which discovered important considerations to include in the nest box, vents for air flow, shade, and the size of the opening for the bird to enter the nest box. These are additional areas that can be added and subtracted as students are constructing their boxes. My students have used this skill in find the area of irregular polygons. This information is included on the checklist, and using this tool will help students to remember to include these features on their plan.
The size of the opening should be between 4-6 centimeters, and the amount of shade should provide 5 centimeters of overhang on sides and over the opening to keep out rain and sun. Vents should be between 1-2 centimeters holes or gaps near the top of the nest box.
Students will continue to design the sides and the roof of the nest box using the dimensions from the base measurements. The computations are written within each area on the grid paper and include markings for where they divided the diagram to use the distributive property, and created smaller rectangular sections to find the area.
Students turn plans into prototypes, as they use their mathematical plans to create a nest box using cardboard or tag board, glue, and tape. Each pair of students will build two nest boxes, so that each student has their own nest box. Because of safety issues and availability of tools and other supplies, the students are using paper and cardboard to build, rather than wood and nails.
The students use the to-scale template, which has been cut out of the centimeter grid paper used for planning, and transfer it to the cardboard by tracing around each section, cutting it out, and constructing the nest box. Together, the students assist each other to attach and support the sides the sides around the base, and then add the roof. Each pair of students will determine their own process for construction, and assistance will be provided by other students as needed. Students are encouraged to share strategies for construction.
The nest boxes will be allowed to dry, to be used the following day when students will analyze the size of the boxes to determine if it meets the criteria of the total surface area between the 625 and 750 square centimeters.