Sylphs are common but spectacular cloud-forest hummingbirds in northern South America.   Adult males have extremely long tails; juvenile males have shorter tails and females look like a different species entirely.  This is the violet-tailed sylph, restricted to the western Andes in Colombia and Ecuador; the more widely distributed but quite similar long-tailed sylph has a striking blue-green tail.   None of these is a fully-adult male, although the bird to the right is close.   These were photographed at about 1600 m elevation in the foothills of Montezuma Peak (Tatama National Park) in southwestern Colombia.