13. Hawai`i Creeper, Oreomystis mana DESCRIPTION AND TAXONOMY The Hawai`i creeper is a small Hawaiian honeycreeper (family Fringillidae, subfamily Drepanidinae) 10.8 to 13.0 centimeters (4.3 to 5.1 inches) in length and 13.7 grams (0.48 ounces) average weight (Lepson and Woodworth 2001). It is predominantly olive green on the back and dull Adult Hawai`i creeper foraging on `ōhi`a greenish-buff below, with a white chin trunk. Photo © Jack Jeffrey. and throat. The brownish-white bill is almost straight, the iris is dark hazel, and the legs and feet are dark brown. Immatures are paler below, with less contrast between the throat and breast, and they usually have a prominent yellowish-white superciliary line. Field identification is complicated by its similarities in appearance and behavior with the Hawai`i `amakihi (Hemignathus virens), Hawai`i `ākepa (Loxops coccineus coccineus), and Japanese white-eye (Zosterops japonicus) (Scott et al. 1979). At the time of European discovery, each of the six main Hawaiian Islands harbored a small, straight-billed, simple-tongued, insectivorous bird. The Hawai`i creeper was first described as Himatione mana by Wilson (1891a). Subsequent nomenclature has been problematic (reviewed in Pratt 1992b, 2001), and the species has variously been considered a full species (Perkins 1903), a subspecies of Paroreomyza bairdi (Bryan and Greenway 1944) and a subspecies of Loxops maculata (Amadon 1950). It is currently classified as Oreomystis mana (American Ornithologists’ Union 1998) following Pratt (1979, 1992b), but recent evidence (Olson and James 1995, Fleischer et al. 2001) supports its inclusion as a full species in the genus Loxops. LIFE HISTORY Hawai`i creepers defend a small, 10 to 20 meter (33 to 66 feet) radius area immediately surrounding the nest, and forage over a 4 to 7 hectare (9.9 to 17.3 acre) home range during the breeding season (Ralph and Fancy 1994a, Revised Recovery Plan for Hawaiian Forest Birds 2-108 VanderWerf 1998b). Females do all or most of the nest building and incubate, brood, and feed the chicks; males assist by feeding the female both on and off the nest and by feeding the young (Sakai and Johanos 1983; VanderWerf 1998b; J. Nelson, U. S. Geological Survey, unpubl. data). During the nonbreeding season, pairs range over a wider area of about 11 hectares (27.2 acres) and join other forest birds in mixed-species flocks (VanderWerf 1998b). The Hawai`i creeper generally feeds on insects, spiders, and invertebrates that are gleaned from the trunks and branches of mature trees (Scott et al. 1986). During the breeding season in Hakalau Forest National Wildlife Refuge, Hawai`i creepers foraged at a mean height of 13 meters (43 feet). Most foraging maneuvers were gleans (59 percent) or hangs (24 percent); they also probed, pecked, flaked, pried, and pulled substrates to obtain prey (n = 579 maneuvers, 35 individuals; U.S. Geological Survey, unpubl. data). Foraging took place primarily on the branches (63.7 percent of maneuvers), trunks (13.3 percent) and foliage (12.4 percent) of live `ōhi`a (Metrosideros polymorpha) and koa (Acacia koa) trees; the remainder of maneuvers were in subcanopy trees (specifically, `ōlapa [Cheirodendron trigynum]), dead trees, or epiphytes (n = 579 maneuvers; U.S. Geological Survey, unpubl. data). Beetle larvae make up a large part of its diet (Amadon 1950, Conant 1981a), but no detailed information on prey taken is available. Nests of Hawai`i creepers have been found from January to August (Sakai and Ralph 1980, Scott et al. 1980, Sakai and Johanos 1983, VanderWerf 1998b, Woodworth et al. 2001), but peak breeding occurs from February to May, and molt occurs from May to August (Ralph and Fancy 1994a, Woodworth et al. 2001). A small proportion (less than 5 percent) of individuals may overlap breeding and molting activities (Ralph and Fancy 1994a, Woodworth et al. 2001). A total of 78 nests of this species have been documented (Sakai and Ralph 1980, Scott et al. 1980, Sakai and Johanos 1983, VanderWerf 1998b, Woodworth et al. 2001). Based on 61 nests found at Hakalau Forest National Wildlife Refuge from 1994 to 1999, Hawai`i creepers generally build cup nests at mid-canopy at about 13 meters (43 feet) in height (range 2.8 to 24 meters [9 to 79 feet]) and about 1.5 meters (5 feet) from the main bole of the tree (range 0 to 4.8 meters [0 to 16 feet]). Most (86 percent) are open cup nests but a few (14 percent) are cavity or pseudo-cavity nests. Clutch size is usually two eggs, nest building Revised Recovery Plan for Hawaiian Forest Birds 2-109 requires 11 to 19 days, incubation 13 to 17 days, and the nestling period is 18 days (Sakai and Johanos 1983, VanderWerf 1998b, Woodworth et al. 2001). Approximately one-third of recorded nesting attempts have been abandoned before egg-laying commenced (33 percent, n = 6, VanderWerf 1998b; 27.9 percent, n = 61, Woodworth et al. 2001). At Hakalau Forest National Wildlife Refuge from 1994 to 1999, daily survival rates of active creeper nests were 0.950 ± 0.011 (standard error), and an average of 1.7 chicks fledged from successful nests (Woodworth et al. 2001). Only a fraction of known-fate nesting attempts are successful (11 percent, n = 9, Sakai and Johanos 1983; 50 percent, n = 6, VanderWerf 1998b; 20.4 percent, n = 49, Woodworth et al. 2001). The relatively high rate of nest failure across studies is alarming, especially given the relatively inaccessible locations where these birds nest. Further study is needed to elucidate the causes of these failures. Data from marked pairs suggest that Hawai`i creepers readily re-nest after failure, and two pairs have been recorded re-nesting after fledging young earlier in the season (U.S. Geological Survey, unpubl. data). Parent Hawai`i creepers feed fledglings for at least 3 weeks post-fledging, but within 1 month of leaving the nest young are foraging independently for food (although still following parents; VanderWerf 1998b, Woodworth et al. 2001). Hawai`i creepers have relatively high annual adult survival of about 73 to 88 percent (Ralph and Fancy 1994a, Woodworth et al. 2001), and juvenile survival of about 33 percent (Woodworth et al. 2001). The high survival rate of Hawai`i creepers in Hakalau in part may reflect the rarity of disease in this high- elevation refugium, above the level of mosquito populations. In general, the reproductive potential of the Hawai`i creeper appears to be low due to its small clutch size, relatively long developmental period, and limited breeding season. This low reproductive potential is exacerbated by the high rate of nesting failures, possibly due to the introduction of mammalian nest predators. High adult and juvenile survival rates may compensate to some extent for low annual productivity, but if disease were to reach the upper elevation rain forests, it could have devastating effects. More detailed demographic data are needed to assess the implications for population persistence of the Hawai`i creeper. Revised Recovery Plan for Hawaiian Forest Birds 2-110 Hawai`i creepers are non-migratory, but during the nonbreeding season they range more widely; the average nonbreeding home range size of 10 Hawai`i creepers was 11.9 ± 7.7 hectares (29.4 ± 19.0 acres) (range 4.3 to 27.1 hectares [10.6 to 66.9 acres]), and individual banded birds have been observed in different locations 1 to 4 kilometers (0.62 to 2.48 miles) apart (VanderWerf 1998b). Snetsinger (1995) observed a Hawai`i creeper in māmane (Sophora chrysophylla) forest 7 kilometers (4.35 miles) from the nearest known population. HABITAT DESCRIPTION Hawai`i creepers are most common in mesic and wet forests above 1,500 meters (5,000 feet) elevation (Scott et al. 1986). The species prefers relatively undisturbed koa/`ōhi`a forests (Sakai and Johanos 1983), and the highest densities occur in areas least modified by logging and grazing (Scott et al. 1986). The largest population (see Range and Status below) exists on the windward slope of Mauna Kea in the vicinity of Hakalau Forest National Wildlife Refuge. Annual rainfall at Hakalau averages 2,500 millimeters (98 inches), and the forest canopy is dominated by `ōhi`a and koa. The subcanopy is composed of `ōlapa, pūkiawe (Styphelia tameiameiae), `ōhelo (Vaccinium calycinum), `ākala (Rubus hawaiiensis), kolea (Myrsine sandwicensis), kāwa`u (Ilex anomala), and Cibotium tree ferns (U.S. Geological Survey, unpubl. data). Hawai`i creepers also have been observed occasionally in māmane forest at higher elevations, and may have been more widespread in this habitat historically (Figure 16; Snetsinger 1995). Hawai`i creeper, along with `akiapōlā`au (Hemignathus munroi) and Hawai`i `ākepa, show a decreasing population density gradient from south to north across three sites in Hakalau Forest National Wildlife Refuge (2.18 ± 0.50 birds per hectare in the south at Pua `Ākala, compared with 0.57 ± 0.23 birds per hectare in the north at Maulua). The causes for the density gradient are not completely understood, but cavity availability was lower in the Pedro area than at Pua `Ākala (Hart 2001), food availability was one-third lower at Maulua than at Pua `Ākala (Fretz 2002), and prevalence of pox virus was higher at Maulua than at Pua `Ākala (VanderWerf 2001a), all of which may partially explain the lower population density to the north. Feral pig sign was negatively correlated with Hawai`i creeper density across the three sites. The frequency of disease epizootics in different sections of the refuge should be investigated. Revised Recovery Plan for Hawaiian Forest Birds 2-111 Revised Recovery Plan for Hawaiian Forest Birds 2-112 HISTORICAL AND CURRENT RANGE AND STATUS In the 1890s, Hawai`i creepers were found in `ōhi`a and `ōhi`a/koa forests throughout the island of Hawai`i, usually above 1,070 meters (3,600 feet) elevation (Perkins 1903).