The primitive koa finch (''Rhodacanthis litotes'') is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

species of

Hawaiian honeycreeper Hawaiian honeycreepers are a group of small, passerine birds endemic to Hawaii. They are closely related to the rosefinches in the genus ''Carpodacus'', but many species have evolved features unlike those present in any other finch. Their great ...

in the subfamily Carduelinae of the family Fringillidae. It is known from fossils on the islands of

Maui The island of Maui (; Hawaiian: ) is the second-largest of the islands of the state of Hawaii at 727.2 square miles (1,883 km2) and is the 17th largest island in the United States. Maui is the largest of Maui County's four islands, which ...

and

Oʻahu Oahu () ( Hawaiian: ''Oʻahu'' ()), also known as "The Gathering Place", is the third-largest of the Hawaiian Islands. It is home to roughly one million people—over two-thirds of the population of the U.S. state of Hawaii. The island of O’ ...

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...

Description

An adult primitive koa finch was slender and had a total length of about . There was probably a small distinct difference between the sexes. Based on fossils, it is known that the adult primitive koa finch had a slightly curved, thick bill. The paper that named the species in 2005 also mentions, "the fossil record of '' Rhodacanthis'' may contain at least one additional

cryptic species In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...

. The difference in aperture of the nasal cavity in the Oahu vs. Maui fossils of ''R''. ''litotes'' suggests that those two populations might be recognized as distinct species if more fossils or genetic data were available for them."

Distribution

Primitive koa finch

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s have been found on

and

. Based on its

disjunct distribution In biology, a taxon with a disjunct distribution is one that has two or more groups that are related but considerably separated from each other geographically. The causes are varied and might demonstrate either the expansion or contraction of a s ...

, the species might have occurred on all of the main islands (except the island of Hawaii and perhaps

Kauai Kauai, () anglicized as Kauai ( ), is geologically the second-oldest of the main Hawaiian Islands (after Niʻihau). With an area of 562.3 square miles (1,456.4 km2), it is the fourth-largest of these islands and the 21st largest island ...

), although more fossils are needed for confirmation. It is believed that it inhabited lowland dry forests and savannas, where dominant plant species included ''ka palupalu o kanaloa'' (''

Kanaloa kahoolawensis ''Kanaloa kahoolawensis'', the ''Ka palupalu o Kanaloa'' or ''kohe malama malama o kanaloa'',USFWS''Kanaloa kahoolawensis'' Species Profile/ref> is a species of flowering plant in the legume family, Fabaceae and is endemic to Hawaii. ''Kanaloa'' ...

''), ''aalii'' ('' Dodonaea viscosa''), ''loulu'' (''

Pritchardia The genus ''Pritchardia'' (family Arecaceae) consists of between 24 and 40 species of fan palms (subfamily Coryphoideae) found on tropical Pacific Ocean islands in Fiji, Samoa, Tonga, Tuamotus, and most diversely in Hawaii. The generic name ho ...

'' spp.), and ''koaia'' ('' Acacia koaia''). Unlike other species of '' Rhodacanthis'', koa ('' Acacia koa'') was not present in significant numbers in its habitat.

Diet

The primitive koa finch was a

granivore Seed predation, often referred to as granivory, is a type of plant-animal interaction in which granivores (seed predators) feed on the seeds of plants as a main or exclusive food source,Hulme, P.E. and Benkman, C.W. (2002) "Granivory", pp. 132 ...

, with a bill adapted to eat the hard seeds and pods of

legume A legume () is a plant in the family Fabaceae (or Leguminosae), or the fruit or seed of such a plant. When used as a dry grain, the seed is also called a pulse. Legumes are grown agriculturally, primarily for human consumption, for livestock f ...

s, especially ''ka palupalu o kanaloa'' (''

'') and ''koaia'' ('' Acacia koaia''). It may have also taken

caterpillar Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths). As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder Sym ...

s and ''aalii'' ('' Dodonaea viscosa'')

berries A berry is a small, pulpy, and often edible fruit. Typically, berries are juicy, rounded, brightly colored, sweet, sour or tart, and do not have a stone or pit, although many pips or seeds may be present. Common examples are strawberries, raspb ...

, as these were observed being eaten by other species in the genus.

Extinction

The koa finches seem to have been driven to extinction by

habitat destruction Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...

, and not by climatic variation nor mosquito-vectored diseases. Koa finches were likely driven out of lowland habitat before or shortly after the time of western contact in 1778. The two species from

(the scissor-billed koa finch and primitive koa finch) might have survived in an upland refugium until the late 19th century, paralleling the fate of the two species from the island of Hawaii (the

lesser Lesser, from Eliezer (, "Help/Court of my God"), is a surname. Notable people with the surname include: * Adolf Lesser (1851–1926), German physician * Aleksander Lesser (1814–1884), Polish painter and art critic * Anton Lesser (born 1952), Bri ...

and greater koa finches). However, the only verified records of the Maui species are from fossils at a lower elevation.

References

BirdLife International 2004. Himatione sanguinea. 2006 IUCN Red List of Threatened Species. Downloaded on 10 July 2007. {{Taxonbar, from=Q7243563 Rhodacanthis Birds described in 2005 Fossil taxa described in 2005 Hawaiian honeycreepers Extinct birds of Hawaii Holocene extinctions Late Quaternary prehistoric birds Taxa named by Helen F. James