Small tree-finch (Camarhynchus parvulus)
|Weight||13 g (2)|
Classified as Least Concern (LC) on the IUCN Red List (1).
The diminutive size and distinctive short, curved beak of the small-tree finch help to distinguish it from the other twelve species of finch that are endemic to the Galapagos (2) (3). Collectively known as Darwin’s finches, these remarkable birds have received a high degree of scientific attention, as the diversity of beak size and shape between the species provides strong evidence for Charles Darwin’s theory of evolution by natural selection (2). The male small tree finch can be readily distinguished from the female by the black colouration of the head, shoulders and chest, which develops over the course of five annual moults. Otherwise, both sexes possess uniform, dull greyish-brown plumage (4).
The small tree-finch can be found on several islands in the Galapagos Archipelago, namely: Isabela; Fernandina; Santiago; Pinzón; Santa Cruz; Santa Fé; San Cristóbal; and Floreana. This species was also previously found on Rábida Island, but is now believed to be extinct (5).
The small tree-finch principally inhabits humid, evergreen forest located between elevations of 300 and 700 metres, but may also be found in arid lowland areas, dominated by deciduous trees, shrubs and cacti (3).
An insect-feeding specialist, the small tree-finch’s curved, grasping bill enables it to deftly pick adult insects and caterpillars from the surface of bark and leaves, and to bite through the bark of twigs and leaf stems to expose insect larvae. Despite its specialisation, this species also consumes fruit, seeds and nectar, particularly during the dry season when these foods may form the major part of its diet (3).
Darwin’s finches usually breed during the hot and wet season when food is most abundant. Monogamous, lifelong breeding pairs are common, although mate changes and breeding with more than one partner have also been observed (2). In order to attract a female, male small tree-finches build dome-shaped nests from which they make courtship song displays. Upon arrival at the display nest, the female either accepts both the nest and the male; accepts the male but not the nest (in which case the pair constructs a new nest); or rejects both. Interestingly, older males are more frequently selected as mates due to the fact that as they age, male small tree-finches become more adept at concealing their display nest amongst vegetation. These nesting sites therefore suffer less predation and are more likely to result in breeding success (4). Generally a clutch of three eggs is laid, which are incubated by the female for about twelve days, and the young brooded for a further two weeks before leaving the nest (2). Nestlings and juvenile Darwin’s finches are frequently preyed upon by the short-eared owl (Asio flammeus), while adults are occasionally taken by Galapagos hawks (Buteo galapagoensis) and lava herons (Butorides sundevalli) (2).
Increasing levels of human activity on the Galapagos are creating significant threats to the islands’ native wildlife. Darwin’s finches, in particular, are vulnerable to habitat destruction, invasion by non-native competitors and predators, and the introduction of diseases such as Avian pox (6). Despite these threats, the small tree-finch is not currently considered to be threatened, as its population is large and not undergoing a major decline (7).
The majority of the Galapagos archipelago forms part of the Galapagos National Park, a World Heritage Site. A management plan is in place for the islands, and the Ecuadorian government and non-governmental organisations are working to conserve the unique biodiversity of the Galapagos (8). More specifically, scientists at the Charles Darwin Research Station are working to improve our understanding of Darwin's finches to ensure their conservation. This includes monitoring of populations and investigating introduced diseases (6).
To learn more about the conservation of Darwin’s finches visit:
- Charles Darwin Foundation:
For more information on this and other bird species please see:
- BirdLife International:
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- Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
- Monogamous: having only one mate during a breeding season, or throughout the breeding life of a pair.
IUCN Red List (July, 2014)