The small tree finch (''Camarhynchus parvulus'') is a species of

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

in the

Darwin's finch Darwin's finches (also known as the Galápagos finches) are a group of about 18 species of passerine birds. They are well known for their remarkable diversity in beak form and function. They are often classified as the subfamily Geospizinae or t ...

group of the

tanager The tanagers (singular ) comprise the bird family Thraupidae, in the order Passeriformes. The family has a Neotropical distribution and is the second-largest family of birds. It represents about 4% of all avian species and 12% of the Neotropica ...

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Thraupidae The tanagers (singular ) comprise the bird family Thraupidae, in the order Passeriformes. The family has a Neotropical distribution and is the second-largest family of birds. It represents about 4% of all avian species and 12% of the Neotropica ...

. It has a grasping beak with curved culmens. Its natural

habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...

s are

subtropical The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Geographical z ...

or tropical dry

forest A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...

s and subtropical or tropical dry

shrubland Shrubland, scrubland, scrub, brush, or bush is a plant community characterized by vegetation dominated by shrubs, often also including grasses, herbs, and geophytes. Shrubland may either occur naturally or be the result of human activity. It m ...

. During the non-breeding season it is known to form large groups with small ground-finches. It is an endemic species to the Galapagos islands and its conservation status has been listed as “Least Concern”. However, bird counts which have been conducted since 1997 have shown a continuous decline in small tree-finch populations in the ''Scalesia'' and agricultural zones of Santa Cruz, where the small tree-finch is most abundant. Small tree-finch counts have remained stable in the transition zone (also quite abundant here) and in the less popular dry and fern zones on Santa Cruz island. A recent study has found that this species is in particularly impacted by the larvae of the parasitic avian vampire fly, ''Philornis downsi''.

Distribution

The small tree finch is found on all the main islands except Española, Genovesa, Marchena, Darwin and Wolf. It was also absent in the most recent census (2017-2018) on Rábida, Pinta and Santa Fé islands.

Mating

Darwin's tree finches build display domed nests and use these to attract mates and for nesting. Male small tree finches will sing close to their nest once it has been built, to attract female small tree finches. When these arrive, they inspect the display nest by entering it. Thereafter they will either choose to accept both the male and the display nest, accept the male but reject the nest (so they will then build a new nest together), or reject both the male and the display nest. Older males build more concealed nests, typically higher within the tree canopy, compared to younger males which reduced predation on the nests. Females preferentially choose to breed with older males with whom they have higher fledging success compared to younger males. In a study by Kleindorfer (2007), predation accounted for 60% of nest loss, making it a strong selective force. Males with high vocal performance, which is predicted by beak morphology, also have higher pairing success. There is also evidence for size-assortative pairing based on beak and tarsus length. Thus multiple factors influence pairing success in small tree finches: male and female body and beak size, male vocal performance, nest concealment, and male age.

Colouration

Small tree finches moult annually. Female small tree finches are grey/brown throughout their lives. Male ground finches are born grey/brown, similar to females, but through a pattern of annual moult, attain a black crown and chin (the upper part of their body). Age difference can be assessed in males by observing the darkness of their crown and chin.

Feeding

The small tree-finch is a mainly insectivorous bird, although has a varied diet. Typically, it gleans arthropods and leaves from bark surfaces, but 42% of its diet consists of vegetable matter (nectar, fruits and seeds).

References

{{Taxonbar, from=Q1086136 Camarhynchus Endemic birds of the Galápagos Islands Birds described in 1837 Taxa named by John Gould Taxonomy articles created by Polbot Taxobox binomials not recognized by IUCN