Small ground-finch (Geospiza fuliginosa)

Description

Small ground-finch fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
• Print factsheet

Small ground-finch description

Motivated by the breadth of morphological variation he witnessed in the Galapagos’ thirteen finch species, Darwin mused that “seeing this gradation and diversity in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends.” ^{(3) (4)}. In accordance with their apparent influence on his theory of natural selection, this group of closely related passerines has come to be known as Darwin’s finches. One of the commonest species of Darwin’s finches is the small ground-finch ⁽³⁾. Like the other ground finches, the adult male plumage of the small ground-finch is completely black while the female is brown and streaked ^{(2) (5)}. Compared to the other ground finches, the small ground-finch has a reduced beak size, making it adept at foraging for small seeds ^{(6) (7)}.

Weight

14 g ⁽²⁾

Small ground-finch biology

Darwin’s finches are distinguished by their highly specialised beaks, which enable each species to occupy a different ecological niche ⁽⁶⁾. The ground finches (Geospiza sp.) feed mainly on the ground and are generally granivorous, but also feed on arthropods and the fruit of Opuntia cacti ^{(2) (6)}. In particular, small ground-finch populations in highland areas, such as on Santa Cruz, tend to spend considerably more time foraging in low vegetation ⁽⁹⁾. With its compact beak, this species is much more efficient at foraging for smaller food items than the other ground-finches, with the very small seeds of Sesuvium edmonstonei and Tiquilia fusca being typical components of its diet ⁽⁷⁾.

Darwin’s finches generally breed opportunistically, with egg-laying being most profuse when rainfall is high and food abundant ⁽²⁾. Pairs are typically monogamous and maintain small territories within which they build a small dome-shaped nest in a bush or cactus. On average each clutch comprises three eggs that are incubated for around 12 days before hatching. The nestlings are mostly raised on insects and leave the nest after about two weeks ⁽⁶⁾.

During the breeding season, competition for resources between different species of finch can be extremely intense. In promoting ever increasing levels of specialisation, competition for resources has been the driving force behind the evolution of Darwin’s finches. This is exemplified by the widely divergent beak sizes of different finch species co-inhabiting one island, compared with much more convergent beak sizes when the same species are isolated from each other on separate islands ⁽⁶⁾.

Small ground-finch range

The small ground-finch is endemic to the Galápagos, where it occurs on the islands of Pinta, Marchena, Floreana, San Cristóbal, Santa Fe, Daphne Major, Santa Cruz, Pinzón, Rábida, Santiago, Fernandina, Española, Isabela, Baltra and Seymour ⁽²⁾.

Small ground-finch habitat

Occurs mainly in the arid lowland zones, dominated by cacti, deciduous shrubs and dwarf trees, but on the elevated islands it is also found in the moist highland forest where Scalesia dominates ^{(5) (8) (9)}.

Small ground-finch status

Classified as Least Concern (LC) on the IUCN Red List ⁽¹⁾.

Small ground-finch threats

In common with much of the Galapagos’ endemic fauna and flora, Darwin’s finches are under threat from habitat destruction, introduced diseases, and invasive predatory species such as rats and cats ⁽¹⁰⁾. However, the small ground-finch is still relatively abundant and is not thought to be undergoing a significant decline ⁽¹¹⁾.

Small ground-finch conservation

For their unique biological diversity and significance, the Galapagos Islands are designated both a National Park and a World Heritage Site. As a consequence, conservation of the islands’ native fauna and flora is a high priority ⁽¹²⁾. Furthermore,scientists from the Charles Darwin Foundation continue to conduct further research on Darwin’s finches in order to ensure their long-term conservation ⁽¹⁰⁾.

View information on this species at the UNEP World Conservation Monitoring Centre.

Find out more

To find out more about the conservation of Darwin’s finches visit:

• Charles Darwin Foundation:
  http://www.darwinfoundation.org

For more information on this and other bird species please see:

• BirdLife International:
  http://www.birdlife.org

Authentication

Glossary

Endemic

A species or taxonomic group that is only found in one particular country or geographic area.

Granivorous

Seed eating.

Monogamous

Having only one mate during a breeding season, or throughout the breeding life of a pair.

Morphological

Referring to the visible or measurable characteristics of an organism.

Passerines

A group of more than 5,000 species of small to medium-sized birds which have widely varied plumage and shape. They all have three toes pointing forward and one directed backward which assists with perching, and are sometimes known as perching birds or song birds.

References

1. IUCN Red List (December, 2008)
   http://www.iucnredlist.org/
2. Grant, P.R. and Grant, B.R. (2007) How and Why Species Multiply: The Radiation of Darwin's Finches. Princeton University Press, Princeton, New Jersey.
3. Sulloway, F.J. (1982) The Beagle collections of Darwin's finches (Geospizinae). Bulletin of the British Museum (Natural History) Historical Series, 43(2): 49 - 94. Available at:
   http://darwin-online.org.uk
4. Darwin, C.R. (1845) Journal of researches into the natural history and geology of the countries visited during the voyage of H.M.S. Beagle round the world, under the Command of Capt. Fitz Roy, R.N. 2nd edition. John Murray, London. Available at:
   http://darwin-online.org.uk
5. Kleindorfer, S. (2007) The ecology of clutch size variation in Darwin's small ground finch: comparison between lowland and highland habitats. Ibis, 149: 730 - 741.
6. Hau, M. and Wikelski, M. (2001) Darwin’s Finches. In: Encyclopedia of Life Sciences. John Wiley & Sons, Chichester.
7. Grant, P.R. and Grant, B.R. (2006) Evolution of character displacement in Darwin’s Finches. Science, 313: 224 - 226.
8. Lack, D. (1983) Darwin’s Finches. Cambridge University Press, UK.
9. Kleindorfer, S., Chapman, T., Winkler, H. and Sulloway, F.J. (2006) Adaptive divergence in contiguous populations of Darwin’s small ground finch (Geospiza fuliginosa). Evolutionary Ecology Research, 8: 357 - 372.
10. Charles Darwin Foundation (April, 2009)
    http://www.darwinfoundation.org/en/galapagos/species/birds/native-endemic
11. Birdlife International (April, 2009)
    http://www.birdlife.org
12. UNEP-WCMC (April, 2009)
    http://www.unep-wcmc.org/protected_areas/data/wh/galapago.html