What is any one of several species of very brilliant South American humming birds, having a very long and deeply-forked tail; as, the blue-tailed sylph (Cynanthus cyanurus) called?

sylph — (Zoöl.) Any one of several species of very brilliant South American humming birds, having a very long and deeply-forked tail; as, the blue-tailed sylph (Cynanthus cyanurus). (Webster's 1913.)

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