Justification of Red List Category
This species is listed as Critically Endangered because it has an extremely small range, restricted to one island, where the population exhibits marked population fluctuations, probably owing to climatic events. The accidental introduction of mammalian predators, non-native pest plants, insects or an avian disease, or a stochastic event such as a hurricane could rapidly bring about its extinction.
VanderWerf (2012) estimated 4,475 ±909 birds, which very roughly equates to 3,000 (2,400-3,600) mature individuals. This is larger than the previous estimate of 1,400-2,400 mature individuals, which was based on an estimate of 2,807 ±744 (95% CI) individuals in March 2007.
The species's numbers are believed to have declined over the period 1967-1996 but fluctuated markedly during that time (Morin and Conant 2002). The population size appeared to be fairly stable from 2009-2011 at 2,400-2,900 birds (VanderWerf et al. 2011), but the 2012 estimate was substantially higher (VanderWerf 2012). Fluctuating numbers and large errors associated with estimates have made it difficult to determine the population trend.
Telespiza ultima once occurred at least on the island of Moloka'i in the Main Hawaiian Islands, but was extirpated in prehistory probably by a combination of predation by introduced mammals and habitat loss (Morin and Conant 2002). Today, this species is restricted to the steep, rocky island of Nihoa in the Northwestern Hawaiian Islands (U.S.A.) (Berger 1972, Morin et al. 1997). Numbers fluctuate (James and Olson 1991, Morin and Conant 2002), although some variation may be due to differences in survey methods and time of year. Numbers on Nihoa have ranged from 6,686 in 1968 to 946 in 1987 (James and Olson 1991, Morin and Conant 2002). The most recent population estimate based on surveys in 2012 is 4,475 (±909, 95% CI) individuals (VanderWerf 2012), which very roughly equates to 3,000 (2,400-3,600) mature individuals.
It occurs in low shrubs and grasses and is evenly distributed across the island (Morin et al. 1997, Gorresen et al. 2016). It feeds on seeds, invertebrates, other plant parts and eggs (Berger 1972, Morin and Conant 2002). It nests in cavities in cliffs, rock crevices or in piles of loose rock (Berger 1972, Morin and Conant 2002). The clutch size is usually three (range 2-5), but little is known about nesting behaviour or success. There is no information on adult survival or movements (VanderWerf 2012).
It is thought that the presence of the introduced grasshopper Schistocerca nitens on Nihoa, and its periodic irruptions which lead to the virtual defoliation of the island, may be a significant threat to the species. Other potential threats include the introduction of detrimental non-native species and diseases, as well as stochastic events (Berger 1972, James and Olson 1991, Morin et al. 1997, H. Baker and P. Baker in litt. 1999), such as droughts, storms and hurricanes. Black rats caused the extirpation of translocated Laysan Finches T. ultima when they arrived on Midway in 1944 (VanderWerf 2012). Fire is a past and potential threat (Morin et al. 1997, J. Lepson in litt. 1999). A few individuals of the invasive weed Cenchrus echinatus were discovered on Nihoa in 2011 and removed (VanderWerf et al. 2011), and little regrowth was observed in 2012 (VanderWerf 2012). This plant reduces habitat quality and so is a potential threat to the species. T. cantans is known to be highly susceptible to mosquito-borne avian poxvirus (Poxvirus avium) and avian malaria (Plasmodium relictum), and considering its close relationship T. ultima is presumably similarly susceptible. Mosquitoes are not known to occur on Nihoa or Laysan, but are present on Midway and all the larger Hawaiian islands and thus are relevant to selecting sites for translocations (VanderWerf 2012).
Conservation Actions Underway
It is listed as endangered under the Endangered Species Act. Nihoa is part of the Hawaiian Islands National Wildlife Refuge and the Papahânaumokuâkea Marine National Monument, and legal access is controlled by a permit system that is restricted largely to biologists, researchers and cultural practitioners. Strict protocols are followed to ensure that permitted visitors do not accidentally introduce new species via seeds, eggs or insects travelling on clothes and equipment. Visiting scientists make regular efforts to control one of the three species of alien plant on Nihoa by hand weeding (Morin et al. 1997). An attempted introduction to French Frigate Shoals in 1967 failed (Berger 1972). A process to evaluate and prioritise potential translocation sites throughout the archipelago for this species (and the other two Northwestern Hawaiian Island passerines) is currently underway. Disease susceptibility may preclude reintroduction of the Nihoa Finch to the Main Hawaiian Islands, and translocation efforts may focus on the Northwestern Islands.
17 cm. Medium-sized finch. Male has yellow head and breast, blue-grey back with tinge of yellow in centre, dark wings and tail with yellow-edged feathers, yellowish-white underparts. Female and juvenile yellow heavily streaked with dark brown on back, head, and breast. Voice Song lively and complex, somewhat canary-like. Call a loud chirp.
Text account compilers
Hermes, C., Benstead, P., Isherwood, I., Stuart, T., Symes, A., Derhé, M., Bird, J.
Baker, H.C., Fretz, S., Baker, P.E., Morin, M., Camp, R., VanderWerf, E., Conant, S., Lepson, J.
BirdLife International (2020) Species factsheet: Telespiza ultima. Downloaded from http://www.birdlife.org on 19/02/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 19/02/2020.