Introduction: How are bird beaks adapted to the foods they eat? In this lab, we will simulate "scramble competition" (just like in the kids game, "Hungry, hungry hippos") between six species of birds in six different environments. Each bird has a different beak type (spoonbill, tweezerbeak, tongbeak, etc.) and you will find that depending on the food available, some will do better than others in each environment. No two environments are the same, and in our simulation, each one has a different primary food source: stick insects (toothpicks) in the vegetation, water bugs (floating styrofoam peanuts) in the "pond", seeds (popcorn kernels) in the field, worms (cut rubber bands) in the soil, etc.
Procedure: Your goal is to compete with the other birds and to gather as much food as possible in each environment. Food items will be "on the ground" (your table or lab bench), and you must use only your assigned "beak" to pick up the food. Food must be picked up off the table, and placed into your "stomach" (your free hand). Your stomach must remain above the level of the table at all times. You may not use your beak for any other purpose than picking up food off the table. For example, you cannot steal food from another bird's beak, nor can you stab the other birds or try to knock food out of their beak. Bodychecking is absolutely verboten! Any violation of the rules will necessitate that you "regurgitate" all of your gathered food. When all of the food is gone, count and record how many food items each bird captured in that environment, put things back as you found them, and then move on to another environment.
Data Entry: Use the table below to record the species (type of beak), environment (type of food), and both the number and percentage of the total food items eaten by each type of bird. Create a bar graph of percent food eaten with 36 bars (a bar for each of the six species in environment 1, env. 2, etc.). Label your graph, and color code the bars for emphasis. Include a legend which indicates the color of each species. Finally, answer the questions.
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Questions:
1. Define the terms "generalist" and "specialist". (Hint-these are not just biology words).
2. Which species was the winner (got the highest percentage of food) in each environment?
3. Assign each of the birds a rank from 1 to 6 within each environment, where 1 represents the most food eaten and 6 represents the least. Now add up all of the ranks for each type of bird. The lowest overall rank is the most successful generalist. Show the total rankings of each of the birds:
4. Does the ranking correctly predict the bird which was the best generalist? Why or why not?
5. A specialist should have a very good (low) ranking in one environment and very poor (high) rankings in all other environments. Show the rankings of a bird which fits this pattern, and circle the environment to which it is specialized.
6. An old saying claims that "a jack of all trades is a master of none." Explain this concept with reference to the bird beaks.
7. The type of bird with the best (lowest) rank in a particular environment will eventually outcompete all others and drive them out of that environment. Why does natural selection in a stable environment favor specialists.
8. What is the advantage of being a generalist? How can generalists compete against specialists? (Hint: think about unstable or changing environments)
9. How does competition for a limited food resource affect the fitness of an organism? (What happens to those who lose and why?)
10. Where will competition be more intense-between members of different species (inter-species) or between members of the same species (intra-species)? Explain.
Learn about the beaks of Darwin's Finches and the beaks of the Hawaiian Honeycreepers