• Summary
• Text account
• Data table and detailed info
• Distribution map
• Reference and further resources

Justification of Red List category
Following methods developed in a series of papers published in 2017 (Akcakaya et al. 2017, Keith et al. 2017, Thompson et al. 2017), the probability that the species is extinct based on records and surveys is 0.984, and the probability it is extinct based on threats is 0.941. Accordingly, it is classified as Extinct. This species has not been recorded with certainty on Kaua'i since 1989 nor on Hawai'i since 1987, and recent searches specifically for it, alongside extensive surveys for other species on both Kaua'i and Hawai'i, have failed to locate it. It was driven to extinction by habitat loss and degradation, introduced rats, cats, pigs and other non-natives, and in particular as a result of avian malaria and avian pox viruses from introduced mosquitoes.

Population justification
There have been unconfirmed reports of Ou up to 1996, but no confirmed records since 1989. Following methods developed in a series of papers published in 2017 (Akcakaya et al. 2017, Keith et al. 2017, Thompson et al. 2017), the probability that this species is extinct based on records and surveys is 0.984, and the probability it is extinct based on threats is 0.941. It is accordingly considered Extinct and the population size is set to 0 mature individuals. Historically Ou were widespread across much of the Hawaiian Archipelago, but were extirpated from O'ahu, Maui, Moloka'i and then Lana'i between 1899 and 1931 (Pyle and Pyle 2017). The last confirmed record on Hawai'i was in 1987 (Snetsinger et al. 1998) while the last confirmed record on Kauai was 1989 (Pyle 1986).

Trend justification
This species is considered extinct. The last confirmed record on Hawai'i was in 1987 (Snetsinger et al. 1998) while the last confirmed record on Kaua'i was 1989 (Pyle 1986).

Psittirostra psittacea was originally widespread in the Hawaiian Islands (USA), but was extirpated from O'ahu, Maui, Moloka'i and then Lana'i between 1899 and 1931 (Snetsinger et al. 1998). On Kaua'i, it survived in the Alaka'i Wilderness Preserve into the mid-1970s, with c. 62 birds being present during 1968-1973 (USFWS 1983), but only a few in 1981 (Scott et al. 1986), two in 1989 and none since. On Hawai'i, several populations were present in the early 1980s, with c.394 estimated during 1976-1983 (Scott et al. 1986) but, in 1984, a lava-flow from Mauna Loa passed through the Upper Waiakea Forest Reserve, the species' stronghold (Scott et al. 1986, Snetsinger et al. 1998). In 1982 and 1992 Hurricanes ‘Iwa and ‘Iniki battered the Alaka'i swamp, the last known range of Ou on Kaua'i, and had devastating effects on the native forest. Three species of bird, including Ou, were not seen on Kaua'i since these hurricanes (USFWS 2022). However, there have been unconfirmed reports from Koai'e Stream, Alaka'i (Kaua'i) and Pu'u Maka'ala Natural Area Reserve and Kapapala-Ka'u Forest Reserve (Hawai'i) up to 1996 (Snetsinger et al. 1998, J. Lepson in litt. 1999).

It was restricted to wet to mesic 'ohi'a forest between 800 and 1,900 m, mainly 1,200-1,500 m (Scott et al. 1986, Snetsinger et al. 1998), though historically range expanded into low-elevation forest (Snetsinger et al. 2020). Its bill was adapted to feeding on 'ie'ie Freycinetia arborea, an understory vine, and outside the 'ie'ie fruiting season, it was nomadic in response to seasonal fruit and invertebrate abundance (Snetsinger et al. 1998).

Since the arrival of humans in the Hawaiian Archipelago, Hawai’i’s forest birds have undergone tremendous losses and face a panoply of threats, primarily; habitat loss and degradation; avian disease; and predation and competition from non-native species. At least 71 taxa of Hawaiian birds had disappeared before the arrival of Captain James Cook in 1778; 24 more have been extirpated since (Banko and Banko 2009a).

With the arrival of the Polynesians between 1000 and 1200 CE, almost all lowland forests were felled and burned to make way for agriculture (Kirch 1982). This loss continued with the arrival of European and American settlers. Forests continued to be cleared until only high-elevation forest remained. Much of the forest that remains has been invaded by non-native species.

Hawai'i has a long history of non-native species. When the Polynesians arrived, they brought with them pigs Sus scrofa, dogs Canis familiaris and Polynesian Rats Rattus exulans. With the Europeans and Americans came Black R. rattus and Brown Rats R. norvegicus, cats Felis catus, mongoose Herpestes auropunctatus, feral goats Capra hircus, cattle Bos taurus, deer Axis axis, more than 50 species of birds (Atkinson and Lapointe 2009), plants, invertebrates, and diseases. Introduced ungulates have altered forest structure through herbivory and the dispersal of invasive plants, rendering it far less suitable for Ou and other forest birds. Rats, cats and mongoose predate both nests and adult birds (Lindsey et al. 2009). Rats also compete with Ou for their primary food source, ‘ie‘ie vine Freycinetia arborea (Banko and Banko 2009b), while non-native birds may also compete with them for resources (Foster 2009).

Non-native avian diseases introduced to Hawai'i are some of the most pervasive threats faced by native birds and are likely to be the main cause of many previous extinctions. Both avian malaria Plasmodium relictum and avian pox Avipoxvirus spp. are transmitted by the Southern House Mosquito Culex quinquefasciatus, currently climatically restricted to elevations below 1,500 m and responsible for the disappearance of many highly susceptible Hawaiian forest birds from elevations below this. The islands of Kaua'i, O'ahu, Moloka'i, and Lānaʻi have no forest above 1500m and therefore offer no refugia from these fatal diseases. Little forest remains above this elevation on Hawai'i and Maui and as the climate warms the elevational range of Culex will increase (Atkinson and Lapointe 2009). Wallows created by feral pigs provide additional breeding habitats for Culex and allow it to infiltrate deeper into forests (Lapointe et al. 2009). By the time avian malaria was thought to have taken hold on Kaua'i in the 1950s Ou were already uncommon and lost from low elevations, suggesting disease is not solely responsible and forest clearance and invasive species also bear considerable responsibility for its decline (L. Crampton in litt. 2023).

For species with already small population sizes, natural disasters can be catastrophic. In 1984 thousands of acres of forest, in one of the species' last strongholds, the Upper Waiākea Forest Reserve, were engulfed by the kilometre-wide lava flow (Reynolds and Snetsinger 2001). In 1982 and 1992 Hurricanes ‘Iwa and ‘Iniki battered the Alaka'i swamp, the last known range of Ou on Kaua'i, and had devastating effects on the native forest. Three species of bird, including Ou, have not been seen on Kaua'i since these hurricanes (USFWS 2022).

17 cm. Chunky finch with thick bill strongly hooked at tip. Male olive-green with sharply defined yellow head and white undertail-coverts. Female olive-green above and below, greyer on throat and upper breast. Bill pink in both sexes. Voice Song long, loud and complex with whistles, trills, and warbles. Call an upslurred or downslurred whistle, very far-carrying.

Text account compilers
Nesbit, D., Vine, J.

Contributors
Camp, R., Fretz, S., Gorresen, M., Pratt, T., VanderWerf, E., Woodworth, B., Lepson, J., Nelson, J., Crampton, L., Stuart, T., Symes, A., Isherwood, I., Bird, J., Benstead, P., Butchart, S., Stattersfield, A., Westrip, J.R.S., Derhé, M. & Jeffrey, J.

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Recommended citation
BirdLife International (2024) Species factsheet: Ou Psittirostra psittacea. Downloaded from https://datazone.birdlife.org/species/factsheet/ou-psittirostra-psittacea on 24/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from https://datazone.birdlife.org/species/search on 24/12/2024.