sexual dimorphism. Males have shorter bills but longer wings and tails than females. Males have bronze-green upperparts with coppery-bronze heads, a discreet white spot behind the eye, dusky throats, metallic green underparts, a dark gray belly, and a forked blackish bronze-green tail. Some males have white on the chin and throat. Females have similar upperparts, but have white underparts and grayish throats and bellies speckled with green. The tail is less deeply forked and is edged grayish white. Juveniles look similar to females. The sword-billed hummingbird is the only known bird whose bill is longer than the rest of the body, excluding the tail. It is black, heavy, and slightly upturned. The extremely long bill helps the species feed on flowers with long corollas that are inaccessible to other species. Vocalizations The sword-billed hummingbird makes a low, guttural, slightly trilled trrr. Habitat and distribution The sword-billed hummingbird is found in the Andes from western Venezuela through Colombia, Ecuador, and Peru to Bolivia. It inhabits humid and wet montane forest, forest edges, shrubland, gardens, and patches of páramo at elevations of , but is most common at elevations of . The species is generally non-migratory, but shows localized movements in Colombia and northwestern Venezuela, where it moves to higher altitudes in the early wet season and returns to lower elevations in the dry season. The sword-billed hummingbird's distribution correlates with the distribution of species of the subgenus Tacsonia in the genus Passiflora, due to its highly specialized bill and feeding habits. Behavior and ecology As is characteristic of hummingbirds, the sword-billed hummingbird can fly backwards and hover in the air. It also exhibits higher than average wing-disk loading than other members of its family. Diet and feeding The sword-billed hummingbird is a specialist feeder, feeding mainly on the nectar of flowers with long corollas, including Brugsmania sanguinea, Datura stramonium, Passiflora mixta, P. pinnatistiplua, P. mollissima and P. sexflora, along with flowers from the genera Aethanthus, Fuchsia, Salpichroa, and Solanum. It probes flowers from below while feeding, and is a trap-line feeder, visiting a specific series of flowers in a regular, consistent sequence. It also hawks for insects, catching flying insects by keeping the bill open. Perching and preening The sword-billed hummingbird perches with its bill angled upwards to reduce the strain of the heavy beak and improve balance. The length of the bill is so long, it also forces the sword-billed