Any of various small, brilliantly coloured birds found in the Americas. The name comes from the sound produced by the rapid vibration of their wings when hovering near flowers to feed. Hummingbirds have long, needlelike bills and tongues to obtain nectar from flowers and capture insects. They are the only birds able to fly backwards. The Cuban bee hummingbird (Mellisuga helenae), the world's smallest bird, is 5.5 cm/2 in long and weighs less than 2.5 g/0.1 oz. There are over 300 species. (Family Trochilidae, order Apodiformes.)
The long cleft tongue of a hummingbird is in the form of a double tube, which can be extended a considerable distance beyond the bill and withdrawn again very rapidly; the sternum (breastbone) is greatly developed, forming a suitable base for the wing muscles; the plumage has a metallic lustre.
Other species include Patagonia gigas, the largest hummingbird, reaching a length of 21 cm/8 in, and inhabiting the Andes from Ecuador to Chile; it is bronze-green, with reddish underparts, and is characterized by the flapping movement of its wings, in place of the usual vibratory movements. Trochilus polytrius, in addition to the iridescent green colouring, has a brilliant red bill and a forked tail of bluish black; Lophornis ornatus, of Brazil, has fawn-coloured tufts with green terminal spots on each side of the neck. Loddigesia mirabilis of Peru is one of the most gorgeous species: the upper plumage is a lustrous bronze green, the underparts are white, the throat is emerald green, rimmed with black, and the head and crest are a vivid blue. The female is green, with white below. Ensifera ensifera, the swordbill, has a straight bill, 12 cm/5 in long, which is more than the length of body and head together.
The species of the genus Phaethornia are sometimes termed ‘the hermits’, because of their more sombre green and brown plumage, and also from their habit of frequenting dark woods and forests. The genus Glaucis includes three species of hermits that are capable of plucking insects from small flowers as well as sucking nectar.