Small ground finch

Appearance

This is the smallest of the ground finches, measuring 11 cm in length . Its beak is short and pointed, with a slightly curved culmen. On average, its beak is smaller than that of the medium ground finch, though there is a significant overlap in size between the two, particularly on islands where only one of the two species exists. On islands where the two species compete directly, the differences between their beaks are greater. The male is black with white-tipped undertail coverts, while the female and young are brown with streaked underparts. There have been observable phenotypic differences between finches that live in lowlands and ones that live in highlands, and this change is most likely attributed to adaptation. The finches seen in highlands have larger, more pointed beaks and smaller feet and claws compared to the lowland variety. These finches are on a cline , and individuals in the hybrid zone have intermediate traits. This is an example of parapatric speciation, where the elevation gradient of 560 meters is causing differentiation in traits, but hybrids are well adapted in their “hybrid zone.”

Status

Although the population size of the small ground finch has not been quantified, it is described as common across the Galápagos, and the International Union for the Conservation of Nature lists it as a species of Least Concern. Its numbers seem to be stable, and neither its population size nor its range size appear to approach thresholds for concern. However, like all endemic wildlife on the Galápagos Islands, it is impacted by some human activities, including fires, overgrazing by domestic and feral animals, and the introduction of exotic species. It is found in ten of the Important Bird Areas established on the islands. The species suffers from high mortality rates from the parasitic fly, ranging from 16% to 95% over a four-year period .

Habitat

Like all but one of the other Darwin's finches, the small ground finch is endemic to the Galápagos Islands. Abundant and widespread, it is found on every island in the archipelago except Genovesa, Wolf and Darwin. It is most common in arid coastal and transition areas, though it moves into the highlands following the breeding season.

Food

Like the other Galápagos ground finches, the small ground finch is an omnivore with a preference for vegetable matter. It feeds primarily on the ground or in low vegetation, eating seeds, buds, flowers, leaves and the occasional insect. It forms symbiotic relationships with Galápagos tortoises and both marine and Galápagos land iguanas, gleaning parasites from their skins.

Predators

Although the population size of the small ground finch has not been quantified, it is described as common across the Galápagos, and the International Union for the Conservation of Nature lists it as a species of Least Concern. Its numbers seem to be stable, and neither its population size nor its range size appear to approach thresholds for concern. However, like all endemic wildlife on the Galápagos Islands, it is impacted by some human activities, including fires, overgrazing by domestic and feral animals, and the introduction of exotic species. It is found in ten of the Important Bird Areas established on the islands. The species suffers from high mortality rates from the parasitic fly, ranging from 16% to 95% over a four-year period .