Darwin's Finches

Eco-Tour

By Karey Fuhs

The 13 species of Darwin’s Finches (genus Geospiza, pinzón) that are found in the Galápagos are perhaps the most famous and sought-after land birds on the islands, given the ecological significance of differences in species’ beak morphology and its link to feeding behavior. All of the finches are sparrow-sized with mottled gray, brown, black, or greenish feathers and short, rounded wings. Because all 13 species have similar superficial characteristics, it is difficult to impossible (even for naturalist guides) to distinguish them. The only clues they provide are the shape of their beak, the type of food they eat, and the type of habitat they occupy.

Although they all originated from a single ancestor, individual species have formed as niche specialists: some eat seeds, some eat leaves, some eat cactus, some eat insects. One species found on Wolf drinks the blood of Nazca or red-footed boobies, a habit that has led to its being dubbed a “vampire finch.” Three other finch species—the small, medium, and sharp-billed ground finches—have the distinction of eating the ticks and mites off of reptiles. There are even two species—the woodpecker and mangrove finches—that use twigs or spines as primitive tools to extract hidden insect larvae or grubs from holes in trees branches.

The mating season of finches generally begins after the first major rainfall of the rainy season (around February). The male courts the female by building an elaborate dome-shaped nest made of twigs, grass, bark, feathers, and other materials, which he locates in his firmly-established and highly protected territory. The male will continually attend to the female at the nest, while she lays and incubates her eggs (two to five, on average), and during the first weeks of the fledglings’ lives.

Finches are found on all major islands, with each species distributed throughout the archipelago (and within islands) according to its desired habitat.