The Crimson Sunbird (Aethopyga siparaja), is a sunbird that is part of group of very small Old World passerine birds. Crimson Sunbird is a resident breeder in tropical southern Asia from India to Indonesia and the Philippines.
Crimson Sunbirds are tiny, only 4.33 inches long. They have medium-length thin down-curved bills and brush-tipped tubular tongues, both adaptations to their nectar feeding. The adult male has a crimson breast and maroon back. The rump is yellow and the belly is olive. The female has an olive-green back, yellowish breast and white tips to the outer tail feathers. The call is chee-cheewee.
Crimson Sunbirds feed largely on nectar, although they will also take insects, especially when feeding young. Flight is fast and direct on their short wings. Most species can take nectar by hovering like a hummingbird, but usually perch to feed most of the time. Two eggs or three eggs are laid in a suspended nest in a tree. This species is found in forest and cultivation.
The Crimson Sunbird is the national bird of the Republic of Singapore.