Large tree-finch  (Camarhynchus psittacula)

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

The large tree-finch is one of thirteen finch species endemic to the Galapagos Islands, collectively known as Darwin’s finches, which each possess markedly different bill shapes and sizes (3). Such differences helped Charles Darwin to formulate his theory of evolution, and provide some of the most convincing evidence for “evolution in action” (2). This species possesses a large, powerful bill, with a thick base and a markedly down-curved culmen (3) (4). The male can be readily distinguished from the female by the black colouration of the head, shoulders and chest, which develops over the course of several annual moults (3) (5). Otherwise, both sexes possess uniform, dull olive-green plumage (3).

The large tree-finch can be found on several islands in the Galapagos Archipelago, namely: Isabela; Santa Cruz; Santa Fé; Fernandina; Santiago; Floreana; Marchena; and Pinta. This species was also previously found on the islands of Pinzón and Rábida, but is now believed to be extinct (3).

The large 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 (4) (6).

The remarkable diversity of beak forms amongst Darwin’s finches allows each species to feed in a specialised way (7). With its curved, powerful beak, the large-tree finch is capable of biting through the bark of twigs, exposing adult insects and larvae such as caterpillars, which are then consumed (4). While invertebrates form the major part of its diet, this species will also consume fruit, especially during the dry season (4).

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. Breeding pairs maintain small territories, in which they construct a small dome-shaped nest with an entrance hole in the side. 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. The short-eared owl (Asio flammeus), frequently preys on the nestlings and juvenile Darwin’s finches, while adults are occasionally taken by Galapagos hawks (Buteo galapagoensis) and lava herons (Butorides sundevalli) (2).

Like other bird species endemic to the Galapagos, the large tree-finch is affected by ongoing habitat destruction, invasive species, and introduced diseases, such as avian pox (7). Nevertheless, despite being uncommon in some parts of its range, the global population of this species is not considered to be small enough, nor undergoing a sufficiently significant decline, to warrant a threatened classification (6).

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 (7).

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

To learn 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