Hawaiʻi ʻelepaio

The Hawaii elepaio (Chasiempis sandwichensis), also Hawaiian elepaio, is a monarch flycatcher found on the Big Island of Hawaii. Until 2010, all three elepaio species, the Kauaʻi ʻelepaio (Chasiempis sclateri), the Oʻahu ʻelepaio (Chasiempis ibidis) and this species were considered conspecific.

Taxonomy and systematics
The Hawaii elepaio was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it with the flycatchers in the genus Muscicapa and coined the binomial name Muscicapa sandwichensis. Gmelin based his description on the "sandwich flycatcher" that had been described in 1783 by the English ornithologist John Latham in his book A General Synopsis of Birds. Latham had examined a specimen from the Sandwich Islands (now the Hawaiian Islands) in the collection of the naturalist Joseph Banks. The specimen would have been collected between 17 January and 22 February 1779 near Kealakekua Bay on the island of Hawaii during James Cook's third voyage to the Pacific Ocean. The Hawaii elepaio is now placed in the genus Chasiempis that was introduced in 1847 by the German ornithologist Jean Cabanis. The species was formerly considered to be conspecific with the Kauai elepaio (Chasiempis sclateri) and the Oahu elepaio (Chasiempis ibidis). The genus name is derived from Ancient Greek khaskō meaning "to gape" and empis meaning "mosquito" or "gnat".

Subspecies
Three subspecies are recognised which differ in their ecological requirements and head coloration (see also Gloger's Rule):
 * C. s. sandwichensis - (Gmelin, 1789) : The Kona elepaio. It differs from the volcano subspecies by having the forehead and the supercilium whitish with some rusty feathers. It inhabits mesic forest characterized by koa (Acacia koa) and ōhia lehua (Metrosideros polymorpha); its population seems to be stable at about 60,000–65,000.
 * C. s. ridgwayi - Stejneger, 1887 : The volcano elepaio. Originally described as a separate species. This is the most common subspecies today, with a population of around 100,000–150,000, or more than half of the total number of elepaio. It is a bird of the rainforest, which on Hawaii are characterized by ōhia lehua and hāpuu (Cibotium tree ferns).
 * C. s. bryani - Pratt, 1979 : The Mauna Kea elepaio. It is only found in the māmane (Sophora chrysophylla ) – naio (Myoporum sandwicense) dry forest on the leeward slopes of Mauna Kea. It has the entire head heavily washed with white. Due to destruction of most of its habitat, it is the rarest Big Island subspecies, with a population of 2,000–2,500 birds.