Small Tree-Finch (Camarhynchus parvulus)

An insect-feeding specialist, the small tree-finch's curved, grasping bill enables it to deftly pick adult insects and caterpillars from the surface of bark and leaves, and to bite through the bark of twigs and leaf stems to expose insect larvae. Despite its specialisation, this species also consumes fruit, seeds and nectar, particularly during the dry season when these foods may form the major part of its diet (3). Darwin's finches usually breed during the hot and wet season when food is most abundant. Monogamous, lifelong breeding pairs are common, although mate changes and breeding with more than one partner have also been observed (2). In order to attract a female, male small tree-finches build dome-shaped nests from which they make courtship song displays. Upon arrival at the display nest, the female either accepts both the nest and the male; accepts the male but not the nest (in which case the pair constructs a new nest); or rejects both. Interestingly, older males are more frequently selected as mates due to the fact that as they age, male small tree-finches become more adept at concealing their display nest amongst vegetation. These nesting sites therefore suffer less predation and are more likely to result in breeding success (4). Generally a clutch of three eggs is laid, which are incubated by the female for about twelve days, and the young brooded for a further two weeks before leaving the nest (2). Nestlings and juvenile Darwin's finches are frequently preyed upon by the short-eared owl (Asio flammeus), while adults are occasionally taken by Galapagos hawks (Buteo galapagoensis) and lava herons (Butorides sundevalli) (2).

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