More interesting than the woodpecker finch's food is the method these finches use for extracting food from shrubs. Woodpecker finches have evolved their feeding methods to include using small twigs and cactus needles for prying grubs and insects from within the branches of shrubs. Another species of Galapagos finch, the cactus finch, does not typically use twigs or cactus needles for extracting its food, but captive cactus finches have learned the behavior when caged near captive woodpecker finches.
Most finches are seed eaters with prominent conical beaks for cracking and hulling seeds. The woodpecker finch's beak has evolved to a slender shape useful for prying into small holes and crevices. The slender bill of the woodpecker finch is more efficient for holding and maneuvering twigs and cactus needles the birds use for skewering their food. Bird watchers, scientists and tourists visiting the Galapagos Islands can observe woodpecker finches procuring food using the "tools" available to them. Woodpecker finches are one of 13 closely related Galapagos finch species known as Darwin's finches.
Explorer and biologist Charles Darwin was intrigued by the finches inhabiting the Galapagos Islands. The small, nondescript birds are unremarkable in appearance except for pronounced variances in the shapes of their bills. Darwin proposed that the birds' bills changed in response to the need for finding a variety of food in an environment where all types of food are scarce. Some of the seed-eating finches began to expand their diets from seeds to include cactus pulp, insects and even blood. The woodpecker finch's adapted diet of concealed insects and larvae prompted a gradual change of its bill to the woodpecker finch's current slender bill. The woodpecker finch and associated finch species were significant subjects in research leading to Darwin's theory of evolution.
Biologists have documented failures of species too specialized for survival in changing environments. The woodpecker finch has adapted its bill for a specialized diet, and scientists suggest that it could not compete with species with more efficient methods of procuring the same food. The nuthatch and brown creeper are examples of North American birds that could compete with the woodpecker finch for its food. These birds have longer bills that can procure more concealed food from trees and shrubs without using tools. The singular and specialized features and behavior of woodpecker finches could render them incapable of survival if nonnative competing species are introduced to their habitat.
