Poʻouli

The poʻo-uli was brown above and grayish-white below, with a broad black mask extending behind the eye. Adults were silvery-gray above the mask, shading into brown at the crown, with a bold, pale patch just behind the mask. Juveniles were similar but buffier below with a smaller mask and without gray above. Most published images of the poʻouli are of the juvenile plumage.

Poʻo-uli

The poʻo-uli was discovered in 1973 when students from the University of Hawaiʻi found the bird on the north-eastern slopes of Haleakalā on the island of Maui. It was found during the Hana Rainforest Project at an altitude of 1,980 metres (6,500 ft) above sea level. The poʻo-uli was the first species of Hawaiian honeycreeper to be discovered since 1923.

It was dissimilar to other Hawaiian birds; evidence based on DNA analysis supports it as being the most ancient of all the Hawaiian honeycreeper lineages to survive to recent times, its lineage having split off from the rest of the Hawaiian honeycreepers during the late Miocene, about 5.7-5.8 million years ago. The Hawaiian honeycreeper lineage itself only diverged from its common ancestor with Carpodacus around 7.2 million years ago; this would make the divergence of the poʻouli chronologically closer to the initial divergence from the common ancestor with Carpodacus than to the divergence of most other Hawaiian honeycreeper lineages (aside from the one containing Oreomystis and Paroreomyza, which diverged about a million years after Melamprosops's lineage), most of which diverged after the mid-Pliocene, 3.77 mya. Around the time the poʻouli lineage originated, Ni'ihau and Kauai were the only two large Hawaiian islands in existence (aside from the then-larger Northwestern Hawaiian Islands), indicating that the po'ouli's lineage must have evolved there and eventually spread to Maui Nui at some point after it first arose in the early Pleistocene, with the recent poʻouli evolving on and/or eventually becoming restricted to Maui.[5]

Its diet consisted mostly of snails, insects, and spiders and it nested in native ‘ōhi‘a lehua (Metrosideros polymorpha) forests. Po’ouli relied more on an insectivorous diet because the snails' diets required more foraging.

In the past, at least according to fossil records, it appears that the po’ouli inhabited the drier half of the island of Maui, across the southwestern slope of Haleakalā, at altitudes of 275–1,350 metres (902–4,429 ft).

Fossils show that the po'ouli once lived at Maui’s lower elevations in more arid environments, thriving on a presumed diet of native tree snails, invertebrates, insects and their larvae. The relatively recent arrival of lethal, mosquito-transmitted avian malaria in Hawaii quickly wiped out the low-elevation birds, forcing a rapid relocation, en masse, to higher elevations and mountain rainforests; this move showed a likely avoidance of mosquitoes by the birds. Moving to higher elevations also meant adjusting their diets, coming to avoid flying insects and focus on mollusks and other invertebrates. Overall, the sharp decrease in numbers (and subsequent relocation of survivors) negatively affected the po’ouli’s once-thriving existence, their genetic diversity and population growth, reproduction and overall distribution.[6]

When the species was first discovered, 100–200 poʻo-uli were estimated to exist. There were only 76 birds per km². By 1981, there were only 15 birds per km². By 1985, there were only 8 per km²: from 1975 (when it was first discovered) to 1985, only ten years later, the population had dropped by over 90 percent. In the 1980s, the poʻo-uli disappeared from the easternmost part of its range and was only found in the western branch of the Hanawi Stream.

To preserve the poʻo-uli and other endangered fauna and flora, the State of Hawaii established the 9,500-acre (38 km²) Hanawi Natural Area Reserve. This connected several protected areas to make one larger protective area. This protection effort was only possible due to the work of several groups: the government, Maui County, the National Park Service, The Nature Conservancy, and several private companies. The land was fenced off and by June 1996 they began to clear out the pigs from the closed areas. Four years and 202 pigs later, the poʻo-uli pen was completely cleared of pigs. As more pigs were removed from the other two pens, the population of native species that lived there, e.g. the Maui parrotbill and ʻākohekohe, rose slightly faster than they otherwise would have. Rats, cats, and goats were still being removed from the poʻo-uli pen.

Adult

By 1997, only three individuals were known to exist. These had home ranges within the Hanawi Natural Area Reserve and the adjacent Haleakala National Park.

In 2002, one of these, a female, was captured and taken to a male's home range in an attempt to get them to breed. The female, however, had flown back to her own territory, which was 1.5 miles (2.4 km) away, by the next day. There was also a ten-day expedition in 2004. The goal was to capture the three birds and bring them to a conservation center on the island, with the hopes that they would produce captive-bred offspring.

On September 9, 2004, one of the remaining birds, a male, was captured and taken to the Maui Bird Conservation Center in Olinda, in an attempt to breed the bird in captivity. However, biologists could not find a mate for the male before it died, around two months later, on November 26, 2004.[7]

It is uncertain whether the other two birds that remained at the time were a male and female, or two of the same sex. Since 2004, extensive surveys failed to locate these or any other individual po’ouli, indicating a possible extinction. However, they remained listed as critically endangered by BirdLife International (and thereby the IUCN) until additional surveys had confirmed extinction beyond a reasonable doubt. Tissue samples were taken from the male captured in 2004 for possible future cloning.

The San Diego Zoo in California is one of the few organizations (outside of Hawaii) retaining potentially viable po’ouli genetic material, at their research center, the Frozen Zoo®. This “endangered species databank” is the largest, most expansive of its kind in the world, retaining over 10,000 living cell cultures, germplasm, gametes, oocytes, blood and sperm samples. Furthermore, the Frozen Zoo® retains frozen embryos from well over 1,000 different endangered, vulnerable and threatened species, with one extinct species—the po’ouli. San Diego has had many previous successes with samples stored in their Frozen Zoo®, through in vitro oocyte maturation and fertilization, surrogacy, artificial insemination, and embryo transfer techniques, to name a few; for example, the artificial insemination of several rare species of Asian pheasant with cryopreserved sperm resulted in successful egg-laying, hatching healthy chicks.

The po’ouli’s dramatic population decline has been attributed to a number of factors; habitat loss from human activities, mosquito-transmittted disease, native habitat degradation caused by introduced Indian axis deer, predation by feral pigs, rats, cats, and especially the small Asian mongoose have all contributed. An overall decline in the native tree snails (due to many of the same factors) that the poʻouli relied on for food has also been a leading cause in their disappearance.

In 2019, after continued habitat degradation, presence of disease and invasive species, and a long period with no sightings, the IUCN classified the po’ouli as extinct.[8] On September 29, 2021, the U.S. Fish and Wildlife Service declared the Poʻouli extinct and the species was delisted from the Endangered Species Act on October 16, 2023.[9]

• List of recently extinct birds
• List of extinct animals of the Hawaiian Islands
• Holocene extinction

• "Poʻo-uli - BirdLife Species Factsheet". BirdLife International. 2007. Retrieved 2007-09-28.
• Phalen, D.N.; Groombridge, J. (2003). "Field research in Hanawi: A story about working with the world's most endangered bird". Journal of Avian Medicine and Surgery. 17 (17): 39–42. doi:10.1647/1082-6742(2003)017[0039:FRIHAS]2.0.CO;2. S2CID 85651457.
• Pukui, Mary Kawena; Elbert, Samuel H. (1986). Hawaiian Dictionary. Honolulu: University of Hawaiʻi Press. ISBN 0-8248-0703-0.
• VanderWerf, Eric A.; Groombridge, Jim J.; Fretz, J. Scott; Swinnerton, Kirsty J. (2006). "Decision analysis to guide recovery of the poʻouli, a critically endangered Hawaiian honeycreeper" (PDF). Biological Conservation. 129 (3): 383–392. doi:10.1016/j.biocon.2005.11.005.
• Baker, P.E. (1998). "A description of the first live Poouli captured". Wilson Bulletin. 110 (3): 307–310.
• Baker, P.E. (2001). "Status and distribution of the Poouli in the Hanawi Natural Area Reserve between December 1995 and June 1997". Studies in Avian Biology (22): 144–150.
• Baldwin, P.H.; Casey, T.L.C. (1983). "A preliminary list of foods of the Poouli". Elepaio (43): 53–56.
• Casey, T.L.C.; Jacobi, J.D. (1974). "A new genus and species of bird from the Island of Maui, Hawaii (Passeriformes: Drepanididae)". Occasional Papers. Bernice P. Bishop Museum (24): 216–226.
• Engilis Jr., A. (1990). "Field notes on native forest birds in the Hanawi Natural Area Reserve, Maui". Elepaio (50): 67–72.
• James, H.F.; Olsen, S.L. (1991). "Descriptions of 32 new species of birds from the Hawaiian Islands: Part II. Passeriformes". Ornithological Monographs (46): 1–88. doi:10.2307/40166713. JSTOR 40166713.
• Kepler, C.B.; Pratt, T.K.; Ecton, A.M.; Engilis Jr., A.; Fluetsch, K.M. (1996). "Nesting behavior of the Poouli". Wilson Bulletin (108): 620–638.
• Mountainspring, S.; Casey, T.L.C.; Kepler, C.B.; Scott, J.M. (1990). "Ecology, behavior, and conservation of the Poouli (Melamprosops phaeosoma)". Wilson Bulletin (102): 109–122.
• Olson, S.L.; James, H.F. (1991). "Descriptions of 32 new species of birds from the Hawaiian Islands: Part I. Non-Passeriformes". Ornithological Monographs (45): 1–88. doi:10.2307/40166794. JSTOR 40166794.
• Reynolds, M.H.; Snetsinger, T.J. (2001). "The Hawaii Rare Bird Search 1994-1996". Studies in Avian Biology (22): 133–143.
• Scott, J.M.; Mountainspring, S.; Ramsey, F.L.; Kepler, C.B. (1986). "Forest bird communities of the Hawaiian Islands: their dynamics, ecology, and conservation". Studies in Avian Biology (9).

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• Species factsheet – BirdLife International
• Article in the Honolulu Star-Bulletin about the poʻouli
• BBC storyAttempts to save the Poʻouli, The Guardian 4 May 2022.