Male Chasiempis sandwichensis sandwichensis
The Hawaiʻi ʻelepaio (Chasiempis sandwichensis) is a species of monarch flycatcher found on the Big Island of Hawaii. Formerly, all three ʻelepaio species, the Kauaʻi ʻelepaio, (Chasiempis sclateri), the Oʻahu ʻelepaio, (Chasiempis ibidis), and this species were considered conspecific.
The three subspecies on the Big Island differ in their ecological requirements and head coloration (see also Gloger's Rule):
- Chasiempis sandwichensis bryani, the Mauna Kea ʻelepaio, 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.
- Chasiempis sandwichensis ridgwayi, the volcano ʻelepaio. 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 ʻelepaio. It is a bird of the rainforest, which on Hawaiʻi are characterized by ʻōhiʻa lehua and hāpuʻu (Cibotium tree ferns).
- Chasiempis sandwichensis sandwichensis, the Kona, ʻelepaio. 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 ʻōhiʻa lehua (Metrosideros polymorpha); its population seems to be stable at about 60,000–65,000.