Green Warbler Finch

Although many Darwin's finch species are insectivorous, only the warbler finch appears to be capable of taking prey on the wing. In addition, this species will use its thin, pointed bill to probe amongst moss, bark and leaves for spiders and insects (5). Darwin's finches usually breed during the hot, 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).

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 its unique biodiversity (9). 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).

With its remarkably warbler-like appearance and behaviour (3), it is not surprising that, during his famous visit to the Galapagos, Charles Darwin erroneously classified this species (2) (4). It was only following investigations of Darwin's specimen collection by John Gould, that the warbler finch was discovered to be one of thirteen species of finch endemic to the Galapagos, which would later become known as Darwin's finches. Each of Darwin's finches has evolved a distinct beak shape in order to exploit different food sources (2). The warbler finch possesses a thin, probing bill, finer than that of the other species, which is ideal for feeding on small insects (5). The plumage of the warbler finch is unremarkable, with uniform dull, olive-grey feathers found in both sexes (4). Although recent studies indicate that there are in fact two separate species of warbler finch, the green warbler finch (Certhidea olivacea) and the grey warbler finch (Certhidea fusca), they are assessed together as a single species, Certhidea olivacea,on the 2008 IUCN Red List. Despite having little difference in appearance, they are genetically distinct and occupy different islands in the Galapagos (6).

The green warbler finch is only found in the Scalesia Zone, a lush, humid evergreen forest dominated by the daisy tree (Scalesia pedunculata), which occurs between elevations of 300 and 700 metres (5) (6). In contrast, the grey warbler finch inhabits the arid zone, where the vegetation comprises scattered deciduous trees, shrubs and cacti (5).

The most widespread of all Darwin's finches, the warbler finch is found on every major island in the Galapagos. The green warbler finch mainly occupies larger, inner islands of the archipelago, while the grey warbler finch inhabits the smaller, outer islands (6).

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

Increasing levels of human activity on the Galapagos are causing 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 (7). Despite these threats, the warbler finch is not currently considered to be threatened, as its population is large, and not undergoing a major decline (8).

The green warbler-finch (Certhidea olivacea) is a species of bird, one of Darwin's finches in the tanager family Thraupidae. Sometimes classified in the family Emberizidae, more recent studies have shown it to belong in the tanager family.

When Darwin collected it in 1835 during the Beagle survey expedition he mistakenly thought it was a wren, but on return to England he was informed in March 1837 by the ornithologist John Gould that the bird was in the group of finches.

It is endemic to the Galápagos Islands, Ecuador. This species is closely related to the grey warbler-finch, and were formerly considered conspecific, but both species differ in appearance, distribution, habitat, and song. The green warbler-finch consists of only one subspecies, the nominate olivacea, from Santiago, Rábida, Pinzón, Isabela, Fernandina, and Santa Cruz. Green warbler-finches have a greenish coloration to blend into their lusher semihumid forest habitats, as well as distinctive reddish throat patches on breeding males.

Its natural habitats are subtropical or tropical dry forests, subtropical or tropical moist montane forests, and subtropical or tropical dry shrubland.