The Wilson Journal of Ornithology 124(4):675 681, 2012 
REOCCURRENCE OF ‘OMA‘0 IN LEEWARD WOODLAND HABITAT 
AND THEIR DISTRIBUTION IN ALPINE HABITAT ON 
HAWAIT ISLAND 
SETH W. JUDGE," JACQUELINE M. GAUDIOSO, 11 
P. MARCOS GORRESEN. * 1 2 * 4 AND RICHARD J. CAMP 2 
ABSTRACT.—The endemic solitaire. 'Oma'o (Myttdcsles ohsvurus), is common in windward forests of Hawaii Island, 
but has been historically extirpated from leeward forests. The last detections of ‘Oma’o on the leeward side of the island 
were in woodland habitat on the western Hank of Manila l.oa in 1978. ‘Oma'o were detected in woodland habitat in 
relatively low densities during a 2010 forest bird survey of Hawaii Volcanoes National Park The source of the population 
is unknown. It is probable they originated from a documented but unsurveyed population of ‘Oma’o in scrub alpine lava. 
Alternatively, the birds may have persisted undetected for nearly 35 years, or expanded from windward mesic forests on 
southeast .Vlauna Loa. There is no evidence ’Oma'o recolonized the wet mesic forests of leeward Manna l.oa. The ’Oma’o 
can occupy diverse native habitats compared to other species in the Hawaii Mvudestes genus, of which most species are 
now extinct. The connectivity of each population is not understood hut we assume there are significant geographic, 
physiological, and behavioral barriers for scrub alpine and wet mesic forest populations. The expansion of ’Oma’o to 
leeward woodlands is encouraging as the species is Hawaii Island's Iasi native frugivore capable of dispersing small and 
medium sized seeds of rare angmsperrm. and could have an important role in re-establishing ecosystem function. Received 
27 February 2012. Accepted 2S June 2012. 
Myadesies species in Hawaii have had severe 
population declines throughout all of the main 
Hawaiian Islands. Three of the five endemic 
solitaires are now extinct (Pyle 2002) with 
'Oma'o (Myadestes obscurus) and Puaiohi ( M. 
palmeri) still extant on Hawaii and Kauai 
islands, respectively (Snetsinger ct at. 2005. 
Gorreson el al. 2009). The Kama'o (M. invades 
tinus) was once considered the most common 
forest bird on Kauai but declined sharply in the 
early 1900s and was last observed in I9S5 
(Gorreson et al. 2009). Oloma'o (A/, latwiensis ) 
was once common in Molokai. Lanai, and Maui 
(Wakelee and Fancy 1999). The Oloma'o was last 
detected on Molokai in 1980 (Scott et al. 1986), 
became extinct sometime in the 1930s or 1940s on 
Lanai (Munro 1964). and was last seen on Maui 
in the 1860s (Perkins 1903). The ‘Amaui (M. 
woaltensis) has been extinct on O'ahu historically 
(Boyer 2008). 
‘Oma'o on Hawaii Island have experienced a 
significant island-wide range contraction in the last 
' Hawaii-Pacific Islands Cooperative Ecosystem .Studies 
Unit, University of Hawaii at Hilo, 200 West Kawili. Hilo. 
HI 96720. USA. 
Hawaii Cooperative Studies Unit. University of 
Hawaii at Hilo. P. (). Box 44. Hawai i National Park. HI 
96718, USA. 
1 U.S. Geological Survey. Pacific Island Ecosystems 
Research Center. P. O. Box 44, Hawaii' National Park. 
HI 96718. USA. 
4 Corresponding author; e-mail: sjudge@hawaii.edu 
100 years, and is now distributed across <30% of 
its former range (van Riper and Scott 1979. Scott 
ct al. 1986). 'Oma'o populations are generally stable 
in wet and mesic forests in northeastern, central, and 
southeastern pans of Hawaii Island (Gorresen et al. 
2009). Windward abundances are highest in pro¬ 
tected state and federal lands where feral ungulates 
have been controlled, reducing the negative impact 
to native plant species that provide foraging 
opportunities for this frugivore (Camp et al. 2010). 
‘Oma'o have been considered extirpated from 
all leeward (western) forests since the early 1900s 
(van Riper and Scott 1979, Gorresen ei al. 2009). 
Habitat degradation is thought to be the primary 
cause of the 'Oma'o decline in its leeward 
distribution (Wakelee and Fancy 1999). but the 
causes of the large-scale extirpation are uncertain. 
The threats limiting Hawaiian honeyereepers are not 
as pervasive in limiting ‘Oma'o distribution and 
abundance. Avian malaria (Plasmodium relictum) 
prevalence is high in stable windward ‘Oma'o 
populations (Atkinson and LaPointe 2009), and 
‘Oma'o in captivity quickly recover from experi¬ 
mental exposure to single infectious mosquito bites 
(Atkinson et al. 2001). Introduced predators such as 
rats (Rattiis spp.) and feral cats (Fells catits) can 
cause significant reductions in native bird species 
(Berger 1972. Atkinson 1977, Scott et al. 1986); 
however, the impact of predators on ‘Oma'o is 
unknown. 
'Oma'o are non-migratory, exhibit strong site 
fidelity, and are highly sedentary in forests (Ralph 
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