The Black-backed Thornbill (Chalcostigma herrani) is a small hummingbird endemic to Colombia. With an average body length of 7-8 cm and weight of 3-4 grams, it is one of the smallest hummingbirds in the world. This diminutive bird inhabits the understory and edges of cloud forests at elevations between 1800-3000 meters in the Andes Mountains.
Physical Description
The black-backed thornbill has vibrant, iridescent plumage typical of hummingbirds. The male has a velvety black head, back, and tail, with a bright rufous belly and vent. Females are similar but less vibrantly colored, with grayish undersides and greenish upperparts. Both sexes have a short black bill and bright red eyes. The thornbill’s name comes from the distinctive pair of sharp racquet-shaped feathers on the male’s tail. Females lack these elongated tail feathers.
Diet and Feeding
Like all hummingbirds, the black-backed thornbill feeds on floral nectar and small arthropods. Its long, specialized tongue allows it to dart in and out of flowers to lap up nectar. Favorite nectar sources include flowers from the genera Fuchsia, Barnadesia, Passiflora, and Bromelia. The thornbill supplements its diet by catching tiny insects like gnats and spiders in midair or gleaning them from foliage. It prefers to feed in the middle canopy strata within its Andean forest habitat.
Unique Adaptations
Several unique adaptations allow this tiny bird to survive in the cool, windy conditions of high-elevation cloud forests. Its compact, rounded body minimizes surface area and heat loss. Dense, soft plumage provides insulation against cold temperatures. Short wings allow highly maneuverable flight in cluttered forest environments. The thornbill can reduce its metabolic rate and enter torpor to conserve energy overnight when food is scarce. It is also territorial and aggressively defends flower patches as feeding territories.
Reproduction and Nesting
The breeding season for the black-backed thornbill runs from April to August. Males perform elaborate courtship displays, flying in u-shaped patterns to impress females. Once paired, the female builds a delicate cup nest out of plant down, spider webs, and lichen on a low branch or tree fork. She lays two tiny white eggs and incubates them for 15-19 days. Chicks fledge about 20-26 days after hatching. Males do not participate in nesting duties.
Conservation Status
The black-backed thornbill has a restricted distributional range but is fairly common within its range. Its population is estimated at 10,000-100,000 mature individuals and is currently stable. Habitat loss from deforestation poses the biggest threat. The species is classified as Least Concern by the IUCN Red List. Protection of remaining cloud forest habitat will be key to the long-term survival of this unique Andean hummingbird. With its dazzling colors and remarkable adaptations, the black-backed thornbill is a jewel of biodiversity we must take care to preserve.