The ʻapapane (/ˌɑːpɑːˈpɑːneɪ/ AH-pah-PAH-nay;) is a small, crimson species of Hawaiian honeycreeper endemic to the Hawaiian Islands. They are the most abundant and widely distributed honeycreeper and are found on the islands of Hawaiʻi, Maui, Lānaʻi, Kauaʻi, Molokaʻi and Oʻahu.

ʻApapane commonly forage in the canopies of ʻōhiʻa (Metrosideros polymorpha) trees, drinking nectar from the flowers and serving as important pollinators. Hawaiians primarily used red feathers from ʻiʻiwi, but also some from ʻapapane, to adorn the ʻahuʻula (capes), mahiole (helmets), and nā lei hulu (feather leis) of aliʻi (Hawaiian nobility).

Description
ʻApapane are small at 5.1 in when fully grown. They are sexually dimorphic in size: male ʻapapane have a mass of 16 g (0.56 oz), while females average 14.4 g (0.51 oz). Adult ʻapapane are overall bright crimson, with distinct white undertail-coverts and lower abdomen feathers. They have black primaries and retricies. Juvenile ʻapapane are yellow-brown and gray, with the same white plumage as adults, and molt into crimson plumage over the course of two years. 'Apapane are often seen in a tail-up posture, showing off their white feathers.

Song
'Apapane are active singers, including in flight. There is considerable variation in their calls and songs, but phrases are often repeated. They are known to sing at a perch for 10-30 second intervals, and their song may include repeated squeaks, whistles, rasps, melodic trills, and clicking sounds.

Source
Wikipedia