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From National Science Education Standards: Populations and ecosystems
Have you ever thought about the differences between a hummingbird and a hawk? They are both birds and yet they look nothing alike! Why do you think they look so different?
Aside from hawks being very big and hummingbirds being very small, these two birds exhibit other differences. Take their beaks, for example. A hawk’s beak is razor sharp and can tear the flesh off the small animals it eats. A hummingbird’s beak is long and thin, which helps it dip into the flowers to sip nectar (a sugary fluid the hummingbird uses for food). How can two species of bird have beaks that are so different?
Today we will explore how, in different environments with different food types, specific adaptations, or changes in physical features, are more beneficial than others. You will use common household items and seeds, grains and nuts to mimic how birds might use their beaks to pick up food.
When you look at different bird beaks, you’re seeing a great example of something called adaptation. Adaptations are traits that developed to perform a certain function and allow organisms to thrive in their environment. Although one adaptation might be very useful for a certain species in a specific environment, that same trait might not be useful for another species in a different environment.
To understand how adaptations arise, it helps to understand the process of evolution. Populations of plants, animals and other living organisms change over many, many generations. Scientists call this process natural selection. Natural selection happens in a species when individuals that have traits better adapted for their environment survive longer and have more babies. They pass on the beneficial adaptations to their offspring. So, over the generations these adaptive traits become more common in the population until nearly all individuals in a species have the adaptation.
• Cotton swab
• Binder clip
• Several different kinds of seeds, grains or nuts that differ in size and shape. It is best if you have a wide range: some that are tiny (for instance, grass seeds or couscous), some that are medium-sized (black-eyed peas or lentils), and some that are larger (almonds, cashews, walnuts or hazelnuts).
• Timer with a second hand or clock
• Pen or pencil
• Dampen the cotton swab slightly with water.
• Set out the three types of "beaks" (tweezers, binder clip and dampened cotton swab).
• Place the three different sizes of "food" (small, medium and large seeds, nuts, etc.) in three separate piles (separated by size) on a surface. These three piles will represent different food types; for example, a hazelnut would be a mouse that a hawk might snatch and a grass seed would be a small drop of nectar a hummingbird might eat.
• Place the empty dish within arm's reach.
• Have someone ready to time the activity using the timer.
• Pick up the dampened cotton swab.
• Start the timer for 10 seconds. With the “beak,” collect as many pieces of the biggest "food" as you can and place the pieces in the empty dish.
• How many were you able to collect? (Note this on the paper.)
• Return any pieces of the big food from the dish to their pile.
• Keeping the cotton swab damp, repeat the 10-second "feeding" with the medium-sized food type.
• How many pieces of food could you collect in the dish? Note this on the paper and return the pieces to their pile.
• Now try the damp cotton swab on the smallest type of food for 10 seconds.
• How many pieces were you able to get into the dish? Record this number and carefully place the food back into its pile.
• Repeat these steps with the other two types of beaks—the binder clip and the tweezers—recording the results as you go.
• Which beak did the best at feeding on which foods?
• If only the smallest food were available, which birds in the environment would likely have the most success surviving and reproducing? Would it be the birds with the tweezer "beaks," the cotton swab "beaks," or the birds with the binder-clip "beaks"? What if only the biggest food type were available? How would the tweezer "beak" do if the bird were eating nectar instead of seeds?
• What might happen to the different types of food if one type of bird were to become more common?
Read on for observations, results and more resources.