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Sorting Finch Species
Howard Hughes Medical Institute
Sorting Finch Species
Howard Hughes Medical Institute
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More About Bird Songs
Here is an example of a spectrogram of a human whistle. You can see that a steady frequency produces a horizontal line, and a higher-frequency sound produces a higher line. A sound with a changing frequency gives the line a slope.
Human speech and song are more complicated than a whistle. This is in part because the human voice box, or larynx, is a much more complicated sound-generating organ than the lips. The spectrogram of a song shows many horizontal bands that stack on top of each other, which are called harmonic frequencies.
Birds have a sound-producing organ called the syrinx. It is capable of producing a wider variety of sounds than the human larynx produces, ranging from near-pure tones to very noisy buzzes, as shown on this spectrogram of a song sparrow's song.
A spectrogram, or sonogram, is a visual representation of how sound frequencies change over time. It is generally displayed with the x-axis representing time and y-axis representing frequency.
The intensity of sound is represented by the intensity of the plot, so that on a white background, a very loud sound would appear very dark. Similar sounds and songs produce similar-looking spectrograms.
About Spectrograms
Sorting Finch Species
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Some birds, like ducks and geese, do not learn their vocalizations, whereas passerines, or songbirds, do. Some passerines, including the Galápagos finches, learn their songs only during a very short sensitive period early in life, when they are in the nest being fed by their fathers. Other passerines, such as song sparrows, have much longer sensitive periods for learning songs, which they tend to learn from neighbors rather than their fathers. Yet other passerines, like mockingbirds, learn songs throughout their lives.
About Bird Songs
The Galápagos are a group of islands, or archipelago, about 960 km west of the coast of Ecuador. They are all volcanic in originand formed at different times, from about 0.5 million to 5 million years ago.
Daphne Major is one of the smallest and least accessible islands in the archipelago. It is not, and has never been, inhabited by humans.
Two of the finch species living on Daphne Major are the medium ground finch (Geospiza fortis) and the cactus finch (Geospiza scandens). The birds are similar in size and appearance except for their beaks. The cactus finch has a long, pointed beak capable of probing and opening cactus fruits to eat the seeds. It can also eat the pollen and nectar of cactus flowers. With its shorter, blunter beak the medium ground finch can only eat cactus seeds once they fall to the ground. However, it can also crack open some larger and sturdier species of seeds that the cactus finch cannot open.
Sorting Finch Species
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About Daphne Major
View a map of Daphne Major
Daphne Major in the Galapagos Islands
Above: The Common Cactus Finch
(Geospiza scandens)
Left: The Medium Ground Finch
(Geospiza fortis)
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Sorting Finch Species
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Where are the Galápagos Islands?
Use the + button to zoom in on the Galápagos Islands and specifically Daphne Major.
Sorting Finch Species
Howard Hughes Medical Institute
The finch songs and spectrograms were generously provided by biologists Peter and Rosemary Grant of Princeton University. The Grants have been studying the Galápagos finches for 40 years. Their groundbreaking work is highlighted in the HHMI short film, The Origin of Species: The Beak of the Finch.
The finch photos used in the sorting activity were provided by Michael Dvorak of BirdLife Österreich, Vienna. Additional photos were provided by John Van de Graaff; the Galápagos Islands background photo is from Thinkstock. The song sparrow song file was provided by the Macaulay Library of Natural Sounds and Video.
This interactive was developed by the following individuals:
Writers: Laura Bonetta, Satoshi Amagai, and Dennis Liu
Programmers: Bill Pietsch and Davey Thomas
Graphic design: Bill Pietsch
Human spectrograms: Satoshi Amagai
Scientific consultants: Peter Grant and Rosemary Grant
Teacher consultants: Ann Brokaw and Paul Strode
Additional contributors: Eriko Clements, Sandra Helene Blumenrath, Mark Nielsen, Jennifer Bricken, Chris Vargas, Fabian de Kok-Mercado, Anna Kulow, and Linda Felaco (copyeditor)
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Version 1.0 – Updated on 10/15/14
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Sorting Finch Species
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Geography of the Galapagos
Learn More About Sonograms
Thirteen species of finches live in the Galápagos Islands, all of which evolved from a single common ancestor within the past 2 million to 3 million years. Although they may not seem to be all that different from one another, distinct species living on the same island generally keep to themselves and don’t interbreed. What keeps them separate?
Finches discriminate between members of their own species and those of a closely related species based on appearance and song.
This activity will test your ability to distinguish between two species of finches living on the island of Daphne Major based on these traits.
Sorting Finch Species
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About Daphne Major
About Spectrograms
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Sorting Finch Species
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Only male finches sing. A male bird learns one song, usually from his father. No two males in the same species sing exactly the same song, but songs are similar enough that females can recognize them as their own species. Can you?
To find out, press Start and click on the play buttons that appear next to birds. Then drag the birds to the left or right side of your screen based on their songs. Repeat the process until you have all the finches with similar songs grouped on the same side.
Sort by Song
About Daphne Major
About Spectrograms
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Audio Embeds
Species A
Species B
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Sorting Finch Species
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A spectrogram is a visual representation of sound. If you had trouble sorting the finches by the sound of their songs, it may be helpful to see what the song’s sound looks like. After you click on Continue, a spectrogram will appear on each bird’s silhouette. Now rearrange the two groups of birds so that finches with similar spectrograms are grouped on the same side.
Sort by Spectrogram
To humans, one of the more striking differences among finch species is the shape and size of their beaks. Click Continue to zoom in on the finches’ beaks. Then sort the birds again, based on this characteristic. If you had grouped the birds correctly using previous information, you shouldn’t have to rearrange them at all!
Sort by Beak
Finches can also recognize members of their own species according to body size, shape, and color. But as you will see, the two finch species on Daphne Major don’t appear all that different. Click on Continue to reveal photos of the finches. Then sort the birds again. Does seeing the birds help you group them?
Sort by Appearance
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Reveal Species
To find out how well you could tell the two species apart, click continue and reveal the species names.
About Daphne Major
About Spectrograms
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Howard Hughes Medical Institute
Sorting Finch Species
The 13 species of finches in the Galápagos Islands recognize members of their own species primarily by song but also by appearance.
Which trait allowed you to most easily tell which birds belonged to the same species?
Learn more about the finches you sorted from Daphne Major by pressing the button below and then answer the question on the right.
Conclusion
About Daphne Major
3. Cactus finch (left) and medium ground finch (right)
1. Medium ground finch (left) and cactus finch (right)
2. Medium ground finch (left) and warbler finch (right)
4. Warbler finch (left) and medium ground finch (right)
Here are the beaks of the two finch species you just sorted. Can you identify them?
About Daphne Major
About Spectrograms
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Sorting Finch Species
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Conclusion
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3. Cactus finch (left) and medium ground finch (right)
1. Medium ground finch (left) and cactus finch (right)
2. Medium ground finch (left) and warbler finch (right)
4. Warbler finch (left) and medium ground finch (right)
About Daphne Major
About Daphne Major
About Spectrograms
Credits
The 13 species of finches in the Galápagos Islands recognize members of their own species primarily by song but also by appearance.
Which trait allowed you to most easily tell which birds belonged to the same species?
Learn more about the finches you sorted from Daphne Major by pressing the button below and then answer the question on the right.
Here are the beaks of the two finch species you just sorted. Can you identify them?
Howard Hughes Medical Institute
Conclusion
Sorting Finch Species
Start
3. Cactus finch (left) and medium ground finch (right)
1. Medium ground finch (left) and cactus finch (right)
2. Medium ground finch (left) and warbler finch (right)
4. Warbler finch (left) and medium ground finch (right)
About Daphne Major
Try Again
About Daphne Major
About Spectrograms
Credits
The 13 species of finches in the Galápagos Islands recognize members of their own species primarily by song but also by appearance.
Which trait allowed you to most easily tell which birds belonged to the same species?
Learn more about the finches you sorted from Daphne Major by pressing the button below and then answer the question on the right.
Here are the beaks of the two finch species you just sorted. Can you identify them?
Howard Hughes Medical Institute
Conclusion
Start
Sorting Finch Species
Next
3. Cactus finch (left) and medium ground finch (right)
1. Medium ground finch (left) and cactus finch (right)
2. Medium ground finch (left) and warbler finch (right)
4. Warbler finch (left) and medium ground finch (right)
About Daphne Major
About Daphne Major
About Spectrograms
Credits
The 13 species of finches in the Galápagos Islands recognize members of their own species primarily by song but also by appearance.
Which trait allowed you to most easily tell which birds belonged to the same species?
Learn more about the finches you sorted from Daphne Major by pressing the button below and then answer the question on the right.
Here are the beaks of the two finch species you just sorted. Can you identify them?
Howard Hughes Medical Institute
Sorting Finch Species
Conclusion
Start
3. Cactus finch (left) and medium ground finch (right)
1. Medium ground finch (left) and cactus finch (right)
2. Medium ground finch (left) and warbler finch (right)
4. Warbler finch (left) and medium ground finch (right)
About Daphne Major
Try Again
About Daphne Major
About Spectrograms
Credits
The 13 species of finches in the Galápagos Islands recognize members of their own species primarily by song but also by appearance.
Which trait allowed you to most easily tell which birds belonged to the same species?
Learn more about the finches you sorted from Daphne Major by pressing the button below and then answer the question on the right.
Here are the beaks of the two finch species you just sorted. Can you identify them?
Howard Hughes Medical Institute
Sorting Finch Species
Below are photos of the cactus and medium ground finches with their spectrograms.
Quiz Question 2
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About Spectrograms
1. It's a male cactus finch that learned the medium ground finch song.
2. It's the offspring of a cactus finch father and a medium ground finch mother.
3. It's the offspring of a medium ground finch father and a cactus finch mother.
4. It's a mutant medium ground finch.
Cactus Finch
Medium Ground Finch
About Daphne Major
About Spectrograms
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To learn more about spectrograms and bird songs, press the button below.
You find a finch that looks and sounds like this.
What is the most likely explanation?
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3. It's the offspring of a medium ground finch father and a cactus finch mother.
Sorting Finch Species
4. It's a mutant medium ground finch.
Start
1. It's a male cactus finch that learned the medium ground finch song.
Quiz Question 2
2. It's the offspring of a cactus finch father and a medium ground finch mother.
Next
About Spectrograms
About Daphne Major
About Spectrograms
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Below are photos of the cactus and medium ground finches with their spectrograms.
Cactus Finch
Medium Ground Finch
To learn more about spectrograms and bird songs, press the button below.
You find a finch that looks and sounds like this.
What is the most likely explanation?
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You find a finch that looks and sounds like this.
What is the most likely explanation?
Quiz Question 2
1. It's a male cactus finch that learned the medium ground finch song.
Sorting Finch Species
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4. It's a mutant medium ground finch.
2. It's the offspring of a cactus finch father and a medium ground finch mother.
About Spectrograms
Try Again
3. It's the offspring of a medium ground finch father and a cactus finch mother.
About Daphne Major
About Spectrograms
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Below are photos of the cactus and medium ground finches with their spectrograms.
Cactus Finch
Medium Ground Finch
To learn more about spectrograms and bird songs, press the button below.
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4. It's a mutant medium ground finch.
2. It's the offspring of a cactus finch father and a medium ground finch mother.
Start
1. It's a male cactus finch that learned the medium ground finch song.
Sorting Finch Species
Quiz Question 2
About Spectrograms
Try Again
3. It's the offspring of a medium ground finch father and a cactus finch mother.
About Daphne Major
About Spectrograms
Credits
Below are photos of the cactus and medium ground finches with their spectrograms.
Cactus Finch
Medium Ground Finch
To learn more about spectrograms and bird songs, press the button below.
You find a finch that looks and sounds like this.
What is the most likely explanation?
Howard Hughes Medical Institute
Quiz Question 2
1. It's a male cactus finch that learned the medium ground finch song.
2. It's the offspring of a cactus finch father and a medium ground finch mother.
Sorting Finch Species
4. It's a mutant medium ground finch.
Start
About Spectrograms
3. It's the offspring of a medium ground finch father and a cactus finch mother.
Try Again
About Daphne Major
About Spectrograms
Credits
Below are photos of the cactus and medium ground finches with their spectrograms.
Cactus Finch
Medium Ground Finch
To learn more about spectrograms and bird songs, press the button below.
You find a finch that looks and sounds like this.
What is the most likely explanation?
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Quiz Question 3
If you selected, "It’s a male cactus finch that learned the medium ground finch song," that’s a good explanation.
Sometimes male finches do learn the wrong song. It can happen, for example, when the father dies and they learn the song of a male neighbor of a different species.
If a male finch learns the wrong song, it might mate with the wrong species, provided that their size and overall appearance are not all that different. The offspring of a cactus finch and medium ground finch would look like an intermediate between the two, but the song would not be an intermediate, it would be the same song the male parent sings!
These hybrid offspring are rare, and they are not as fit as either parent. Can you think of why that is?
Sorting Finch Species
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Hybrid Cactus/Medium Ground Finch
About Daphne Major
About Spectrograms
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