Food Web Tangle and Hawks & Rabbits

Post Contributed by Ally Bernstein, Teaching Assistant

Today’s project left us tangled up – in the best way possible. We got up close and personal with the food web for our third day of bird-themed projects brought to us via the Cornell Lab of Ornithology’s BirdSleuth science program.

Ms. Adkins briefly explained the difference between a food chain (which shows energy flow from sun to plants to animals) and a food web (which illustrates the entire flow of energy through many species in an entire ecosystem). Food webs consist of the sun, producers (plants) that use the sun to make food energy, consumers (animals) that eat producers and other consumers, and decomposers (bacteria and fungi) that break down dead plants and animals.

 

Every Beye student was given a card with either the sun, a producer, a consumer or a decomposer.  Instead of humans, we became caterpillars, bacteria, seeds, hawks, domestic cats, beetles, leaves, fungi, robins, hummingbirds, berries, doves, snakes, etc. Using lengths of yarn, students demonstrated the connections between different players in the food web. The sun was connected to all of the producers. The producers were connected to consumers that were herbivores (animals that eat plants) and omnivores (animals that eat plants and animals). Consumers that were carnivores were connected to their prey. And the decomposers were connected to all the plants and animals that they decompose.

As you can see in the photos above, it didn’t take long for things to get pretty complicated! A food web demonstrates how everything in an ecosystem is delicately interconnected. If all of the producers gently tugged their yarn, many consumers and decomposers could feel the pull. If all the decomposers gently tugged, ALL of the consumers and producers could feel the pull, since decomposers are responsible for all nutrient cycling of organic matter.

 

Ms. Adkins then asked for a scenario that affected a single species within the food web. If one species drops out – for example, all ground beetles fall victim to disease and die – many other members of the food web are affected. To demonstrate, the student acting as a  beetle dropped her yarn, and everyone connected to her also dropped their yarn: A seemingly small event can have significant effects on the entire food web! We repeated this once more with a different species and watched our food web fall apart.

 

The second half of this lesson got us outside and moving. We played a game called “Hawks and Rabbits” to connect the food web to the four factors that make a habitat hospitable (food, water, cover and space). It was cold for a May afternoon on the playground, however the children were far too excited by the game to notice. Most of the class became rabbits; two students were hawks. The rabbits had to gather grass (popsicle sticks) and bring it back to their thicket to eat (the domed spider-web structure on the playground). At the same time, the hawks had to tag rabbits and bring them back to their nest (the tree with a bench around it). The first time we ran this three-minute experiment, not many rabbits were able to eat the required amount of food to survive! How could the habitat be adjusted to provide greater balance within this chain?

 

We played again, and this time the food source was closer to the rabbits' cover: a new thicket was found at the bacon bridge, much closer to the food. As a result, some rabbits were able to gather more food. But it was still difficult for many rabbits to evade the hawks. How could the habitat become more favorable for the rabbits' survival?

 

For our third and final play-through, one hawk was removed. With only one predator, many rabbits were able to live successfully. We threw out some additional ways the habitat could be changed to make the game play differently – two thickets! Two places to collect grass instead of one! More rabbits! More nutritious food to sustain the rabbits longer, hence fewer trips to the food source! The important lesson in today's activities is the interconnectedness of living things and the significance of balance within an ecosystem.

We would like to extend a sincere thank you to the Cornell Lab of Ornithology's K-12 Education Department for developing the BirdSleuth curriculum and for offering workshops that help teachers to creatively engage their students with topics and activities such as these presented today!