A denizen of lofty, fog-shrouded mountain rain forests, the Hawai‘i Creeper, formerly called Olive-green Creeper, is a small green bark-picker typically seen creeping along trunks and large branches, peering back and forth, and probing under bark as it searches out its insect prey. The Hawai‘i Creeper was historically widespread and relatively common, but despite its former abundance, no Hawaiian name was ever recorded for this species. Lacking the spectacular bill, brilliant colors, complex songs, and conspicuous behavior of many Hawaiian birds, the drab Hawai‘i Creeper was frequently overlooked and perhaps underappreciated owing to its superficial similarity to the Hawai‘i ‘Amakihi. In fact, Scott Wilson, who collected some of the first specimens in the mid-1880s and described the species shortly thereafter, was unaware that he had encountered a new species until he examined his specimens in England, and consequently had no information about the Hawai‘i Creeper's habits. The first nest was found in 1975, yet the species has only in the past few years become the object of long-term field studies. Despite this neglect, the Hawai‘i Creeper can be quite conspicuous in its limited range when it forms large mixed-species postbreeding flocks with other Hawaiian honeycreepers—the Hawai‘i Creeper's incessant, stuttering dee-dee, dee-dee-dee juvenile calls are among the most characteristic and memorable sounds of summer in its high-mountain refugia.
When the Hawai‘i Creeper was listed as a Federally Endangered Species in 1975, it was not known whether it was merely uncommon or onthe verge of extinction. The epic Hawaiian Forest Bird Survey of the late 1970s and early 1980s found this species to be relatively widespread in higher-elevation ‘öhi‘a and koa forests on the windward side of Hawai‘i Island, however, and estimated a total population of around 12,500 in-dividuals in 4 disjunct populations. No comprehensive surveys have been conducted since that time, but local census data indicate stable populations in at least some protected higher-eleva-tion forests and declines or extirpations in the few lower-elevation sites where the Hawai‘i Creeper had been found.
Most data cited here are from studies at Hakalau Forest National Wildlife Refuge (NWR), located in high-elevation wet and mesic forest on eastern Mauna Kea volcano (Figure 1).