Editor's Note: This account combines coverage of three species of extinct Hawaiian finches: the Greater and Lesser Koa-Finch, and the Kona Grosbeak. The close relationship of these species, and their extinct status, prompted the combined coverage.
These 3 large Hawaiian finches, among the least known of the Drepanidinae, share remarkably similar and dismal histories. All were known historically mainly or entirely from a limited area on the Kona (western, leeward) side of the island of Hawai‘i, although the fossil record shows that the same or closely related species once probably occurred throughout the main Hawaiian islands. All 3 were first discovered by ornithological collectors in the waning years of the nineteenth century, were apparently unknown to native Hawaiians at the time, and disappeared forever in less than a decade following their discovery. There are no credible records of any of the species after the last specimens of each were taken. The only published observations of these birds in life come from Scott Wilson's first and brief exposure to the Kona Grosbeak (Wilson 1888, Wilson and Evans 1890); from Walter Rothschild's collectors Henry Palmer (Rothschild Rothschild 1892b, Rothschild 1893a) and George C. Munro (Munro 1944a); and from the naturalist R. C. L. Perkins (Perkins Perkins 1893b, Perkins 1903). Although these published sources have been cited time and again, because all the species are extinct there is no recourse but to turn to them once more. The present compilation augments these traditional sources with much original data from a thorough check of world museum collections for all extant specimens of the 3 species, as well as with original observations from G. C. Munro's unpublished field journal in the B. P. Bishop Museum, Honolulu (cited throughout this account as “Munro journal”).
The Kona Grosbeak (also called Kona Finch or Grosbeak Finch) was first obtained on 21 June 1887 by Wilson and last collected in September 1892 by Perkins, the period of its historical existence thus lasting 5 years and 6 months. Munro (Munro 1944a: 131), who was evidently the source for the last year of observation given by Berger (Berger 1972b) and Grant (Grant 1995), credits Perkins with encountering this species in 1894, but Perkins made no mention of a sighting in 1894, either in publication (1903) or in his field notes (Banko 1986), and no specimens exist with such a date. Thus Banko (Banko 1986) is correct that the last evidence of the species is from 1892.
Palmer shot the first Greater Koa-Finch (also called Orange Koa-Finch) on 26 September 1891, and Perkins took the last specimens in March 1896, giving the species a historical existence of only 4 years and 6 months, even though it persisted for three and a half years longer than the Kona Grosbeak.
The Lesser Koa-Finch (also called Yellow-headed Koa-Finch) was obtained only by Palmer and Munro, who collected their first specimen on 30 September 1891 and their last on 16 October of the same year, for a total historical existence of only 17 days.
Historically, these 3 species were confined to mesic forests at middle elevations on the drier, leeward slopes of the island of Hawai‘i; only the Greater Koa-Finch was found elsewhere. The Kona Grosbeak was closely associated with the naio, or bastard sandalwood, tree (Myoporum sandwicense) growing on relatively recent ‘a‘a lava; its massive beak, hypertrophied jaw muscles, and “thick tongue like a parrots” (Munro journal: 25 Sep 1891) were adaptations for processing the small, very hard fruits of that plant. The beaks of the koa-finches, as their name implies, were adapted for cutting the green pods of the leguminous koa tree (Acacia koa). The stomachs of the koa-finches were very large and thin-walled for processing large masses of vegetable material, in contrast to the much smaller gastrointestinal tract of the Kona Grosbeak (Perkins 1903, Munro 1944a). All 3 species had the characteristic drepanidine odor “in a marked degree” (Perkins 1903: 440), and the flesh of the koa-finches was also reported to have a strong odor (Munro 1944a). Although each species varied its diet somewhat, the birds were undeniably specialized feeders and doubtless could not have survived in places where their principal food plant was absent.
There is no evidence that native Hawaiians in the nineteenth century had any knowledge of these species. Perkins (Perkins 1893b), followed by Wilson and Evans (Wilson and Evans 1890), applied the name “palila” to the Kona Grosbeak, but this was merely a lapse intended for Loxioides bailleui, to which the name belongs. Of the Greater Koa-Finch, Palmer stated that “natives on Hawaii called the bird ‘poupou' and ‘Hopue,' but did not seem to be well acquainted with it” (Rothschild 1893a: 204), but Perkins (Perkins 1903: 440) considered the accuracy of this statement to be very doubtful, saying that “natives with a really extensive knowledge of the avifauna, to whom the skins were shown, declined to give them a name, and even suggested that they were ‘malihini' (foreign).”
The history of these 3 enigmatic finches, whose discovery was nearly simultaneous with their disappearance, has been the source of considerable wonder. What were the causes of such restricted distributions and almost instantaneous disappearance? In light of the massive loss of species diversity and island populations shown by the fossil record (James and Olson 1991, Olson and James 1991), the extinctions seem less remarkable, a few among many. Perhaps speculation should focus instead on what caused the prolonged survival of these 3 finches in the Kona District of Hawai‘i I., when all other populations of their relatives had long since been extinct.