Is it possible that this incredible diversity could have arisen from just one progenitor species in such a short period of time?Īn international team of scientists, led by Dr Lerner whilst she was a postdoctoral researcher at the Smithsonian Conservation Biology Institute's Center for Conservation and Evolutionary Genetics, set out to answer this question. Some have the bills of parrots, others of warblers, while some are finch-like and others have straight, thin bills", says Dr Lerner. "Some eat seeds, some eat fruit, some eat snails, some eat nectar. The Nihoa finch, Telespiza ultima, dines on birds' eggs, arthropods, flowers and seeds.īut the tremendous diversity of the Hawaiian honeycreepers, which is readily evident in their wide array of bill shapes and sizes, adds to the confusion. Even though the Hawaiian honeycreepers' cardueline sister is not known, scientists point to crossbills, Loxia species (doi: 10.2307/2406551) and the pine grosbeak, Pinicola enucleator (doi: 10.1111/j.) as good examples of closely related species whose behavioural and ecological traits could act as models for how Hawaii may have been colonised. But whether the honeycreepers evolved from just one parental species or several, and whether there was just one colonisation event or several, is debated. Most authorities agree that one (or maybe more than one) species of cardueline finches (Fringillidae: Carduelinae) are the likely progenitors of the Hawaiian honeycreepers. "There were once more than 55 species of these colorful songbirds, and they are so diverse that historically it wasn't even entirely clear that they were all part of the same group," says Heather Lerner, an assistant professor of biology at Earlham College in Indiana and director of the Joseph Moore Museum. Of the handful of species that still survive, six are considered to be critically endangered by the International Union for Conservation of Nature, four more are endangered and five are vulnerable.īut even this severely diminished array of species is informative: evolutionary biologists and ornithologists consider the Hawaiian honeycreepers to be one of the finest examples of adaptive radiation - even more diverse than Darwin's famous Galapagos finches. For example, in 2004, the mysterious snail-eating po'ouli, Melamprosops phaeosoma, became the most recent casualty after the last individual died in captivity. Sadly, like all island-dwelling species, these iconic birds are still going extinct. At least 56 species of Hawaiian honeycreepers known to have existed, although (no thanks to humans), all but 18 of them are now extinct. But each species evolved special feeding habits and a correspondingly special beak shape to fill a different niche found on the specific island within the Hawaiian archipelago. The "typical" Hawaiian honeycreeper - if there is such a thing - feeds on nectar, has brightly coloured plumage and sings a canary-like song. One group of birds endemic to these islands is the Hawaiian honeycreepers. Despite its remote location and geological youth, this chain of islands is bursting with an exuberance of life: plants, insects, birds. In the middle of the Pacific Ocean, thousands of kilometres away from any significantly-sized landmass, lies the Hawaiian archipelago. A juvenile Laysan finch (center), and clockwise from the top: Hawai’i 'akepa, Maui parrotbill, po'ouli, i’iwi, Maui 'alauahio and ʻakiapōlāʻau.
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