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Darwin's Eden

Evolving Beaks

Lizards of the Sea

Masked Killers

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Letter from Alan Alda

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in the classroom

Voyage to the Galapagos:
"Evolving Beaks"

The Frontiers crew treks to Daphne Major, a rugged island called a "laboratory of evolution." By studying and documenting descendents of the finches first collected by Darwin in 1835, scientists are able to observe evolution in action. "Darwin's finches" are a textbook example of how living creatures adapt to their environment.

Curriculum Links
National Science Education Standards
Activity: Design a Better Beak
Think About It!



birds, diversity, evolution





(Please visit the Subject-Area Search feature on this website for related Frontiers shows and activities!)


5-8: Structure and Function in Living Systems; Reproduction and Heredity; Diversity and Adaptations of Organisms
9-12: Molecular Basis of Heredity; Biological Evolution; Behavior of Organisms
5-8: Science and Technology in Society
9-12: Science and Technology in Local, National and Global Challenges
5-8: Science as a Human Endeavor; Nature of Science
9-12: Science as a Human Endeavor


Research and observations during his five-year voyage on the HMS Beagle and especially in the Galápagos inspired Darwin's theories about natural selection and evolution. Back in England in 1836, Darwin began studying the riddle of species variation in barnacles and other animals and plants, as well as the many specimens collected on the voyage.

Since the publication of Darwin's The Origin of Species in 1859, scientists have traveled to the Galápagos to try to prove (or disprove) his theory of natural selection. No one was successful until Rosemary and Peter Grant set up camp in 1973 on Daphne Major, where they witnessed natural selection in action in just a few seasons, as the beaks of several finch species changed size and shape.

The Grants' groundbreaking research demonstrates how beaks in an island population adapt in response to a changing environment. Their remarkable discoveries are chronicled in The Beak of the Finch: A Story of Evolution in Our Time, by Jonathan Weiner.

Back on Daphne Major, we meet some descendents of the birds that came to be known collectively as "Darwin's finches." The 13 finch species in the Galápagos, including the vampire finch, vegetarian finch and others, probably evolved from a common ancestor in the last few million years.

A bird's beak is a tool adapted for survival. Darwin's finches provide a classic example of divergence among closely related species. Each species has evolved its own beak design variation. Some finches have adapted thick, heavy beaks for cracking big seeds; others have tiny, pointy beaks for cracking small seeds or probing flowers and cacti. The woodpecker finch even uses twigs to dig insects out of wood.

  • Obtain samples of different bird foods from supermarkets or pet stores. Choose seeds of varying sizes and shapes. What features do you think would make a bird beak the most effective tool for eating each of the different seeds? Write down a list of helpful features and then design and draw a beak that incorporates those features. Next, find out which birds the seeds are supposed to attract, and see if the beaks you designed match the real bird beaks. Try designing beaks for other functions -- digging grubs out of logs or worms out of the earth.

  • For more details on finch beak design, go to the Destination: Galápagos Islands website, where you'll find sketches of finch beaks, and how they figure into taxonomic keys.

  • Darwin's finches illustrate how one species can diverge and occupy different niches in an ecology. How many different bird species can you find in your environment? Observe birds feeding in your backyard or in a nearby park or aviary. Find examples of different sizes and shapes of bird beaks. Some birds are ground feeders; others will not feed on the ground. Some birds eat seeds; others eat only insects or worms. See if you can determine a relationship between the shape of a bird's beak and what it eats. This activity can also be done by studying illustrations of different birds and comparing their beak shapes and sizes with their preferred food.


  1. Why are the finches in the Galápagos called "Darwin's finches"?

  2. What is meant by "adaptive radiation"? Why is this concept important to an understanding of evolution?

  3. What are the different niches occupied by birds on the Galápagos? How did the scarcity of native insects and land mammals affect the niches occupied by birds?

  4. Following in the footsteps of the Grants, other scientists are researching evolution in action. Use the Web to research current projects in other regions.


Scientific American Frontiers
Fall 1990 to Spring 2000
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