As its common name suggests, the vegetarian finch feeds almost entirely on plant matter, including buds, leaves, flowers, fruits and seeds, although a few insects may occasionally be taken (2) (8) (9). The species also has the unique habit of stripping bark from developing twigs of Croton scouleri in order to reach the sugar-rich insides (9). Feeding takes place mainly in the trees, although the birds may sometimes come to the ground to feed on young leaves and fallen fruit (8).
Darwin’s finches typically breed during the hot and wet season, when food is most abundant, although breeding is opportunistic and closely tied to rainfall (2). Pairs are usually monogamous, but mate changes and multiple mates have also been observed. The nest is usually dome-shaped, with a side entrance, and built out of dry grass in a cactus or bush. The male finch may build a display nest to attract a mate, before both the male and female jointly construct the actual nest (2). Darwin’s finches usually lay around three eggs, which are incubated by the female for about 12 days. The young leave the nest after about two weeks, and the breeding pair may raise several broods each year if environmental conditions are favourable (2). The comparatively small clutches, small-sized eggs and short incubation periods of Darwin’s finches are thought to be adaptations allowing repeated, rapid breeding when conditions allow (10). The breeding pair may maintain a small territory during the breeding season, but often forage in large, mixed-species flocks at other times (2).