The long-tailed sylph (Aglaiocercus kingii) is a species of hummingbird in the Trochilidae family. It is found in Bolivia,Colombia, Ecuador, Peru, and Venezuela. Its natural habitat is subtropical or tropical moist montane forest.
The male long-tailed sylph carries characteristic elongated tail feathers. These feathers are so ridiculously long that they hinder his flight: it is difficult for him to carry such finery every day when he relies on his flying skills to survive. Female sylphs, whose tails are of a more modest size, pick out and mate with the males with the longest tail feathers. They therefore ensure that they are mating with a male who is so fit and healthy that he can live well enough to come into breeding condition even when carrying a heavy load. source