Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Passeriformes Turdidae

Scientific Name: Myadestes obscurus
Species Authority: (Gmelin, 1789)
Common Name(s):
English Omao, Oma'o
Identification information: 18 cm. Small, dull-coloured thrush. Grey-brown above fading to grey on forehead, grey below except for buff undertail-coverts. Juvenile dark brown above heavily spotted with buff, buffy below heavily scalloped with dark brown. Similar spp. Introduced Melodious Laughingthrush Garrulax canorus brighter cinnamon-brown with yellow bill. Voice Song a jerky melody of liquid notes whip-per-weeo-whip-per-weet or an ascending series of twangy notes. Call a cat-like rasp, frog-like croak, or higher "police whistle". Hints Most accessible localities are Hawaii Volcanoes National Park and forest patches along Saddle Road.

Assessment Information [top]

Red List Category & Criteria: Vulnerable D2 ver 3.1
Year Published: 2012
Date Assessed: 2012-05-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Camp, R., Fretz, S., Gorresen, M., Pejchar, L., Pratt, T., VanderWerf, E. & Woodworth, B.
Facilitator/Compiler(s): Benstead, P., Sharpe, C J, Stattersfield, A., Stuart, T., Taylor, J.
Although this species is numerous, it occurs in just two or three areas on Hawai`i, and is classified as Vulnerable on account of its very small occupied range. It is at risk from the effects of exotic taxa. Its present distribution is probably already strongly influenced by the presence of introduced mosquitoes, which spread avian disease.

Previously published Red List assessments:
2008 Vulnerable (VU)
2004 Vulnerable (VU)
2000 Vulnerable (VU)
1994 Lower Risk/least concern (LR/lc)
1988 Lower Risk/least concern (LR/lc)

Geographic Range [top]

Range Description: Myadestes obscurus is endemic to Hawai`i in the Hawaiian Islands (USA) where it formerly occurred almost throughout the island. It is now restricted to the southern and eastern slopes of the island, largely above 1,000 m, c.25-30% of its former range (Scott et al. 1986, Wakelee and Fancy 1999). Here the species is encountered regularly in forests with some native tree component (R. Camp in litt. 2007). The population may be divided by the deforested rangeland of the Kapapala Tract, and a third possibly disjunct population exists above 2000 m on Mauna Loa (Scott et al. 1986, Pratt et al. 1987), where it is widespread in suitable habitat (T. Pratt in litt. 2007). In 1976-1979, it was estimated to total c.170,000 birds (Scott et al. 1986), and thought to exceed that figure in 1995 (Jacobi and Atkinson 1995). At lower elevations there is strong selection pressure for disease resistance, and lineages exhibiting these traits may be expanding (Wakelee and Fancy 1999).

Countries occurrence:
United States
Continuing decline in area of occupancy (AOO): Unknown
Extreme fluctuations in area of occupancy (AOO): No
Estimated extent of occurrence (EOO) - km2: 2600
Continuing decline in extent of occurrence (EOO): Unknown
Extreme fluctuations in extent of occurrence (EOO): No
Number of Locations: 3
Continuing decline in number of locations: Unknown
Extreme fluctuations in the number of locations: No
Lower elevation limit (metres): 300
Upper elevation limit (metres): 3000
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: In 1976-1979, the population was estimated to total c.170,000 birds, and it was thought to exceed that figure in 1995.

Trend Justification:  The species faces stresses from habitat degradation, disease and predation from introduced species; however, at lower elevations there is strong selection pressure for disease resistance, and lineages exhibiting these traits may be expanding (Wakelee and Fancy 1999), thus the current overall trend is unknown.
Current Population Trend: Unknown
Additional data:
Continuing decline of mature individuals: Unknown
Extreme fluctuations: No Population severely fragmented: No
No. of subpopulations: 3 Continuing decline in subpopulations: Unknown
Extreme fluctuations in subpopulations: No All individuals in one subpopulation: No

Habitat and Ecology [top]

Habitat and Ecology: It favours mesic and wet native forests, but is also found at much lower densities in scrub and savanna habitats, especially where `ohi`a and koa trees are present. It occurs in some areas where introduced plants dominate, but is absent in others, its range being negatively correlated with the widespread exotic banana poka. It feeds primarily on fruit and berries, but also on insects (especially caterpillars), snails and fleshy flower bracts of the `ie`ie vine (Berger 1972, Scott et al. 1986). The species plays an important role as a seed disperser of native plants and its absence from areas where it once occurred may be limiting the regeneration of native understorey (L. Pejchar in litt. 2007).

Systems: Terrestrial
Continuing decline in area, extent and/or quality of habitat: Unknown
Generation Length (years): 4.5
Movement patterns: Not a Migrant

Threats [top]

Major Threat(s): Habitat clearance for firewood, timber, croplands and pasture inevitably caused considerable contractions in this species's range, with most forests below 800 m having been converted to agricultural or urban uses. The spread of feral ungulates into native forests has caused habitat degradation, and in some areas non-native plants have replaced the natural habitat (USFWS and Hawai`i Forest Bird Recovery Team 1982, Loope and Medeiros 1995). Feral pigs are particularly disruptive and facilitate the spread of introduced, disease-carrying mosquitoes (USFWS and Hawai`i Forest Bird Recovery Team 1982, Anderson and Stone 1993). Pigs also damage and destroy understorey plants that provide the fruit resources that the species depends upon (L. Pejchar in litt. 2007). Introduced mammalian predators are a further significant limiting factor (Wakelee and Fancy 1999).

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
It occurs in a number of important and well managed protected areas, such as the Hawai`i Volcanoes National Park (Wakelee and Fancy 1999). During the 1990s, efforts were made to reduce the feral pig population by Hawaiian conservation authorities and private landowners (Anderson and Stone 1993), and control of mammalian predators was being attempted in some areas (Wakelee and Fancy 1999), although this has now ceased (R. Camp in litt. 2007). Reforestation of upland pastures is ongoing (T. Pratt in litt. 2007). There is considerable interest in re-establishing the species on the western slopes of the island (T. Pratt in litt. 2007).

Conservation Actions Proposed
Carry out surveys to obtain an up-to-date estimate for the population size. Monitor population trends through regular surveys. Control mammalian predators, including cats, mongooses and rats, effectively and continuously because of rapid rates of recolonisation and reproduction (Wakelee and Fancy 1999). Eradicate feral ungulates, including cattle and pigs, and exclude them from protected areas of forest (K. Wakelee in litt. 1999). Consider reintroducing the species to several montane sites in the Kau and Kona districts to increase the number of subpopulations, increasing the resilience of the species, and potentially speeding up the recovery of important understorey plants (L. Pejchar in litt. 2007).

Citation: BirdLife International. 2012. Myadestes obscurus. The IUCN Red List of Threatened Species 2012: e.T22708579A39727598. . Downloaded on 04 October 2015.
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