The Purple-backed Thornbill (Chalcoparia ruficervix) is a small hummingbird found in the rainforests of Central and South America. With an average body length of only 8-9 cm and a weight of 2-3 grams, it is one of the smallest hummingbird species in the world. Despite its tiny size, the purple-backed thornbill exhibits some remarkable adaptations that allow it to survive and thrive in its tropical habitat.
The most distinctive feature of the purple-backed thornbill, as its name suggests, is the vibrant purple patch on its back and rump which contrasts sharply with its otherwise green plumage. The crown and throat are golden-green, while the underparts are whitish-grey. The long, thin bill is black above and reddish below. The legs and feet are also blackish. The male and female purple-backed thornbills look similar, except the female has slightly duller plumage overall. Juveniles resemble the adults, but have buffy edges to their plumage.
Habitat and Distribution
The purple-backed thornbill is found from Nicaragua south to Bolivia and central Brazil. Its habitat consists of tropical evergreen rainforests as well as semi-deciduous forest and second growth woodland. It has a scattered distribution throughout this range at elevations up to 1200 m. Purple-backed thornbills occur singly or in pairs and are territorial, with the male aggressively defending his territory from intruders.
Like all hummingbirds, the purple-backed thornbill feeds on nectar taken from a variety of brightly colored, scented tropical flowers such as heliconias, Costus, aloes and bromeliads. It uses its long, specialized tongue to lap up the nectar while hovering in front the flower. The bill is perfectly adapted to probe into cup-shaped or long tubular blossoms. The purple-backed thornbill will also hawk small insects on the wing, consuming an important source of protein to fuel its supercharged metabolism.
Courtship and Breeding
During courtship, the male purple-backed thornbill performs elegant aerial displays, flying in repeated elliptical loops to impress the female. Once paired, the female builds a tiny cup nest out of plant down and spider webs, attached to a low horizontal branch or tree fern. She lays two tiny white eggs which she incubates alone for 15-19 days. The chicks are fed regurgitated food by the female and fledge after only 18-23 days, remarkably fast development for such a small bird. Both parents continue to care for the fledglings for a couple of weeks as they learn to forage on their own.
The purple-backed thornbill exhibits some remarkable physiological and behavioral adaptations for its survival in the rainforest ecosystem. Its wings can beat up to 70 times per second, allowing it to precisely maneuver through dense vegetation while foraging. Its heart rate can reach as high as 1,260 beats per minute during flight. The purple-backed thornbill enters a state of torpor at night, lowering its metabolic rate and body temperature to conserve energy when not feeding. This is a critical adaptation for surviving on limited resources.
The purple-backed thornbill has a couple of unusual behavioral quirks as well. It is known for taking “dust baths”, fluffing its feathers while tossing fine dirt and particles over its body, presumably for feather maintenance and parasite removal. It also partakes in “anting”, rubbing crushed ants over its plumage which is thought to act as an insecticide.
Status and Threats
While the purple-backed thornbill remains fairly common throughout most of its range, habitat loss is an increasing threat, especially at the northern end of its distribution. Deforestation for agriculture, logging and cattle ranching destroys the plant and insect food sources on which this species depends. Climate change and drought may also impact its status in the future. As with many Neotropical hummingbirds, strict habitat protection will be needed to ensure the long-term survival of the purple-backed thornbill.
The diminutive purple-backed thornbill exhibits some truly astonishing adaptations for a bird that weighs about the same as a penny. Its unique coloration, agile flight, extreme metabolism and bizarre behaviors make it a true marvel of evolution. As development and climate change further threaten its delicate tropical habitat, increased conservation efforts for this and similar hummingbird species will be key. The purple-backed thornbill serves as an important reminder that even the smallest creatures have an important role to play in maintaining biodiversity. Their intrinsic value deserves to be recognized and protected.