Is chocolate for the birds?
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Featured scientist: Skye Greenler from Colorado College
Background:
About 9,000 years ago humans invented agriculture as a way to grow enough food for people to eat. Today, agriculture happens all over the globe and takes up 40% of Earth’s land surface. To make space for our food, humans must clear large areas of land, which creates a drastic change, or disturbance, to the habitat. This land-clearing disturbance removes the native plants already there including trees, small flowering plants, and grasses. Many types of animals including mammals, birds, and insects depend on these native plants for food or shelter. Large scale disturbances can make it difficult to live in the area. For example, a woodpecker bird cannot live somewhere that has no trees because they live and find their food in the trees.
However, some agriculture might help some animals because they can use the crops being grown for the food and shelter they need to survive. One example is the cacao tree, which grows in the rainforests of South America. Humans use the seeds of this plant to make chocolate, so it is a very important crop! Cacao trees need very little light. They grow best in a unique habitat called the forest understory, which is composed of the shorter trees and bushes under the large trees found in rainforests. To get a lot of cacao seeds for chocolate, farmers need to have large rainforest trees above their cacao trees for shade. In many ways, cacao farms resemble a native rainforest. Many native plant species grow there and there are still taller tree species. However, these farms are different in important ways from a native rainforest. For example, there are many more short understory trees in the farm than there are in native rainforests. Also, there are fewer small flowering plants on the ground because humans that work on cacao farms trample them as they walk around the farm.
Typical cacao farm with some taller trees remaining to provide shade for the cacao.
Undisturbed rainforest. In the rainforest, all the taller trees and small flowering plants remain.
Skye out in the field counting birds along one of her four transects. She spent 4 days along each transects, for a total of 16 days in both cacao fields and rainforests.
Skye is a biologist who wanted to know whether rainforest birds use the forest when they are disturbed by adding cacao farms. Skye predicted she would see many fewer birds in the cacao farms, compared to the rainforest. To measure bird abundance, she simply counted birds in each habitat. To do this she chose one rainforest and one cacao farm and set up two transects in each. Transects are parallel lines along which the measurements are taken. She spent four days counting birds along each transect, for a total of eight days in each habitat. She had to get up really early and count birds between 6:00 and 9:00 in the morning because that’s when they are most active.
Scientific Question 1: What is the effect of cacao farms on bird abundance?
After Skye counted up the abundance data, she broke her abundance data down to look more closely at four groupings of birds:
1. Toucans (Eat: large insects and fruit from large trees, Live: holes in large trees)
2. Hummingbirds (Eat: nectar from flowers, Live: tree branches and leaves)
3. Wrens (Eat: small insects, Live: small shrubs on the forest floor)
4. Flycatchers (Eat: small insects, Live: tree branches and leaves)
Scientific Question 2: What is the effect of cacao farms on the abundance of different bird types?
Scientific Data:
1. What data will you graph to answer the two scientific questions?
Independent variable:
Dependent variable:
2. Make a graph using your selected variables, and screenshot it below:
Interpret the Data:
3. Add up the total amount of birds for each Habitat to answer scientific question 1. Make a claim that answers scientific question 1 – What is the effect of cacao farms on bird abundance?
4. Scientific question 1: What evidence was used to write your claim? Reference specific parts of the tables or graph.
5. Scientific question 1: Explain your reasoning and why the evidence supports your claim. Connect the data back to what you learned about how agriculture may act as a disturbance.
After exploring scientific question 1, Skye was shocked to see so many birds in cacao farms! She decided to take a closer look at her data. Skye wanted to know how the types of birds she saw in the cacao farms compared to the types of birds she saw in the rainforest. She predicted that cacao farms would have different types of birds than the undisturbed rainforest. She thought the bird types would differ because each habitat has different types of food available for birds to eat and different types of plants for birds to live in.
6. What is the hypothesis? Find the hypothesis in Skye’s next steps (above) and paste it below. A hypothesis is a proposed explanation for an observation, which can then be tested with experimentation.
7. Make a claim that answers scientific question 2 – What is the effect of cacao farms on the abundance of different bird types?
8. Scientific question 2: What evidence was used to write your claim? Reference specific parts of the table or graph.
9. Scientific question 2: Explain your reasoning and why the evidence supports your claim. Connect the data back to what you learned about diet and living preferences of the different types of birds.
10. Scientific question 2: Did the data support Skye’s hypothesis? Use evidence to explain why or why not. If you feel the data were inconclusive, explain why.
Your next steps as a scientist:
11. Your next steps as a scientist: Science is an ongoing process. What new question(s) should be investigated to build on Skye’s research? What future data should be collected to answer your question(s)?
*Teachers can request an answer key through the form below.
This dataset and content is provided our by our friends at Data Nuggets.
Visit DataNuggets.org to see the original activity and additional materials
