Darwin’s finches: Part Two
The discovery of a new bird to science in a distant archipelago is providing evidence of how, in the absence of competitors, unique species can evolve rapidly to fill empty niches. But the archipelago is not the Galapagos, and the bird is not one of Darwin’s finches.
In the year of the 200th anniversary of Darwin’s birth, a paper in the leading scientific journal, Ibis, describing a new bird species in the Solomon Islands, has reinforced evidence that white-eyes evolve new species faster than any other known bird family –including Galapagos finches.
The new species has been named Vanikoro White-eye Zosterops gibbsi. The formal description was published in Ibis by Dr Guy Dutson of Birds Australia (BirdLife in Australia), who led a recent expedition to the island of Vanikoro to gather evidence about the bird. Its scientific name gibbsi is in honour of the first person to see the species – David Gibbs.
Vanikoro White-eye differs from other family members by having a distinctively shaped bill; along with different leg and eye-ring colours.
Vanikoro is a small island in the south-west Pacific, in the Solomon Islands archipelago. The rugged volcanic island with steep, forest-covered hills was visited by Jules D’Urville in 1829 – six years prior to The Beagle landing in the Galapagos – who collected specimens of Vanikoro Flycatcher Myiagra vanikorensis and Uniform Swiftlet Collocalia vanikorensis.
“Genetic research has shown that white-eyes evolve new species faster than any known bird family,” said Guy Dutson. “Islands only 3 km apart in the Solomons have their own white-eye species, and the Solomon Islands alone have 13 species of white-eye.
“Like Darwin’s finches, these birds have evolved unique beak structures and feeding behaviours in the absence of competitors”, Dr Dutson added.
White-eyes are small sociable birds of tropical forests. As their common name implies, many have a conspicuous ring of tiny white feathers around their eyes. The Vanikoro White-eye differs from the geographically closest white-eye, the Santa Cruz White-eye Z. sanctaecrucis, by having a longer bill, and different leg and eye-ring colour.
Vanikoro White-eyes are found in forest habitats, mostly above 350 m, and feed on insects and small fruits. “Vanikoro White-eyes were abundant towards the summit of the highest mountain”, noted Dr Dutson, who observed an active nest during his expedition. “Up to three adults fed chicks at a single nest, suggesting cooperative breeding, which has only been documented in two other white-eye species”.