Medium tree-finch  (Camarhynchus pauper)

Classified as Critically Endangered (CR) on the IUCN Red List (1).

The medium tree-finch is one of Darwin’s finches, a group of 13 birds endemic to the Galapagos Islands that helped Charles Darwin formulate his theory of evolution. The medium tree-finch is mostly greyish-brown, with whitish or yellowish underparts. The sexes differ in the colour of their head; the female’s is greyish-brown whilst the male’s is blacker (2). All of Darwin’s finches evolved from a single species, but now each possess a specialized bill, adapted to their habitat and diet. The three tree-finch species all have a sharp, grasping bill, and it is believed that the medium tree-finch may be a hybrid of the large and small tree-finches (3).

Endemic to Floreana in the Galapagos Islands, Ecuador (2) (4).

Occurs in montane evergreen and tropical deciduous forest and in humid scrub, generally over elevations of 100 meters (2).

With its specialized bill, the medium tree-finch feeds on insects, nectar, young buds and leaves, by probing crevices in tree bark and searching under twigs and foliage (2).

The medium tree-finch used to be found on the coast, but is now restricted to the highlands (4), as a result of the extensive habitat destruction and degradation on Floreana, caused by agriculture and free-ranging livestock. Introduced predators such as cats, dogs and rats also pose a threat (2). The introduction of diseases, such as avian pox, may also potentially threaten finches. A population of the large ground finch has already become extinct on Floreana, which illustrates the vulnerability of finch species to such threats.

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 (5), all of which will help ensure the future of this species. 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 (3). However, in 2009 the IUCN upgraded the medium tree-finch from Vulnerable to Critically Endangered in light of its tiny range on a small island, and indications of a rapid decline in the species due to the effects of a parasite, Philornis downsi (2).

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

For more information on conservation in the Galapagos, see:

• Charles Darwin Foundation:
  http://www.darwinfoundation.org/english/pages/index.php

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

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