DARWIN FINCHES

About

They are also known as the Galápagos finches.

They are a group of about 18 species of passerine birds. 

Out of 18 birds 17 are endemic to the Galapagos Islands. 

The 18th is found on Cocos Island, Costa Rica and it is called the Cocos finch.

They are small land birds.

Note:

Passerines are birds that have three toes forward, one backward.

For example, parrots have two toes pointing forward and two pointing backward, while emus have three toes pointing forward.

Family

They are classified under the subfamily Geospizinae or tribe Geospizini.

They are not the true finches and they belong to the tanager family.

American dull-coloured grassquit is the closest known relative of the Galápagos finches.

Note: The tanagers comprise the bird family Thraupidae, in the order Passeriformes. 

The family represents about 4% of all avian species.

Adaptive Radiation

Darwin's finches are a classic example of adaptive radiation, a process in which a single species rapidly diversifies into many new forms.

Characteristics of adaptive radiation in Darwin's finches: 

Rapid adaptation 

Darwin's finches adapted quickly to the challenging environment of the Galápagos Islands.

Ecological diversification 

The finches diversified ecologically, which resulted in a variety of phenotypes, including different beak types, body sizes, plumages, feeding behaviors, and song types.

Natural selection 

Adaptive radiation is made possible by natural selection.

Natural selection is a process that explains how populations of organisms change over time in response to environmental changes or competition.

Distribution

The Galápagos Islands and the Cocos Island are the only two areas where they are found.

Distinguishing feature

They are popular for their remarkable diversity in beak form and function.

The size and shape of their beaks are highly adapted to different food sources. These different shapes and sizes differentiates the finches.

Evolution

They are not true finches.

They are thought to have evolved from grassquit that came to the islands from mainland South America more than a million years ago.

Size

The birds have a size varying from 10 to 20 cm and they weigh between 8 and 38 grams. 

The warbler-finches are the scales finches and the largest is the vegetarian finch. 

Species

IUCN Status

Green warbler finch (Certhidea olivacea)

Vulnerable

Grey warbler finch (Certhidea fusca)

Least Concern

Mangrove finch (Geospiza heliobates)

Critically Endangered

Woodpecker finch (Geospiza pallida)

Near Threatened

Large tree finch (Geospiza psittacula)

Vulnerable

Medium tree finch (Geospiza pauper)

Critically Endangered

Small tree finch (Geospiza parvula)

Least Concern

Large ground finch (Geospiza magnirostris)

Least Concern

Medium ground finch (Geospiza fortis)

Least Concern

Small ground finch (Geospiza fuliginosa)

Least Concern

Española  cactus finch (Geospiza conirostris)

Vulnerable

Common cactus finch (Geospiza scandens)

Least Concern

Sharp-beaked ground finch (Geospiza difficilis)

Least Concern

Vegetarian finch (Platyspiza crassirostris)

Least Concern

PRACTICE QUESTION

Q.Consider the following statements about the “Galápagos finches” recently seen in the news: 

1. They are sea birds.
2. They are popular for their remarkable diversity in beak form.
3. They are found only in Galápagos Islands.

How many of the above statements is/are incorrect?

A.Only one

B.Only two

C. All Three

D.None

Answer: B

Explanation:

Statement 1 is incorrect: 

Also known as the Galápagos finches, Darwin's finches are a group of about 18 species of passerine birds. 

17 of which are endemic to the Galapagos Islands. The 18th finch is the Cocos finch which is found on Cocos Island, Costa Rica.

They are small land birds.

Statement 2 is correct: 

They are popular for their remarkable diversity in beak form and function.

The differences between species can be identified by the size and shape of their beaks, which are highly adapted to different food sources.

Statement 3 is incorrect: 

Apart from the Cocos finch, which is from Cocos Island, the others are found only on the Galápagos Islands.