The Rufous-capped thornbill (Chalcostigma ruficeps) is a small hummingbird found in the northern Andes mountains of South America. With an average body length of 7-8 cm and weight of 3-4 grams, it is a tiny bird, though relatively large for a hummingbird. The male has a striking reddish-orange cap on its head, with a bronze-green back and whitish underparts. The female is similar but has a slightly duller cap. This colorful little bird lives in montane forest and scrubland habitats between 2000-4800 m elevation.
Diet and Feeding
The rufous-capped thornbill, like all hummingbirds, has a high metabolism and must feed frequently to fuel its energetic lifestyle. It feeds mainly on nectar from flowering plants and supplements its diet with small insects and spiders. Its long, slender beak allows it to reach nectar deep inside flowers. Some favorite nectar sources include the flowers of fuchsias, lupines, and other montane plants. The bird uses its straw-like tongue to lap up nectar while hovering in front of flowers. It also hawks flying insects, plucking them out of the air with precise aerial maneuvers.
Reproduction and Life Cycle
The breeding season for rufous-capped thornbills depends on latitude and altitude, occuring between February to June in Colombia and August to December in Ecuador. Males perform elaborate courtship displays, flying in U-shaped or figure-8 patterns to impress females. They utilize specialized tail feathers that produce whirring and clicking sounds during these displays. Once a female chooses a mate, the pair builds a delicate cup-shaped nest out of plant fibers, spider webs, and moss. It is attached to a vertical twig or fern frond up to 15 feet above ground.
The female lays just two tiny white eggs in the nest. She incubates them alone for 14-19 days until hatching. The chicks are fed regurgitated food by the female and fledge in about 3 weeks. The young are able to reproduce the following year. Predators of eggs and young include tree snakes and birds like the chestnut-capped brushfinch. Adult hummers are also sometimes caught by larger birds such as falcons or shrikes. Overall though, the rufous-capped thornbill is numerous and not considered threatened.
The rufous-capped thornbill possesses specialized anatomical and physiological adaptations that enable its unique lifestyle and survival in the Andes. It has rapid wing-beat of around 70 beats per second, allowing sustained precise flight and hovering. Rotating wrists permit easy maneuverability. Its feathers lack barbules, resulting in a fuzzy appearance that helps maintain body heat in cold montane environments.
Long incubation periods mean parental care is crucial. The female possesses unique stomach enzymes to produce ‘crop milk’ to feed hatchlings. A rapid metabolism generates high body heat, requiring frequent feeding as mentioned above. Countercurrent heat exchange in its legs also helps conserve warmth. The long, slender bill and extensible tongue let the bird probe into flowers. Excellent vision facilitates food-finding and predator avoidance in dense habitats. The thornbill’s small size means it can survive on limited resources. Overall, this species demonstrates amazing specialization for life on the wing in harsh mountain conditions.
Behavior and Ecology
The rufous-capped thornbill is solitary or seen in pairs most of the year, with occasional gatherings at favored nectar sources. Males are highly territorial, using wing trills and aggressive chases to advertise and defend feeding areas of around 0.5 hectares in size. Their habitats range from scrubby clearings, forest edges, and ravines to more open agricultural areas. This habitat flexibility helps them take advantage of nectar sources provided by flowering crops like quinoa.
A variety of plants depend on the thornbill for pollination services in turn. The bird’s high mobility allows it to regularly patrol and feed from favored perches. It alternates active feeding periods with resting periods where it enters torpor to conserve energy. At night, it enters a deeper sleep state, lowering its metabolism and body temperature significantly. Roosting occurs hidden in dense vegetation. Despite its small size, the rufous-capped thornbill migrates seasonally, moving to lower elevations in winter. This mobility allows it to follow changes in flower availability. Overall, the species fills an important ecological niche as a pollinator and energetic nectar feeder in Andean habitats.
The rufous-capped thornbill is currently categorized as a species of Least Concern by the IUCN Red List. Its population numbers and range size are still relatively large, with an estimated extent of occurrence of 260,000 km2. While some local declines have occurred, the species as a whole appears stable. However, potential threats include habitat loss from deforestation, agricultural expansion, and grazing activity. Climate change may also pose a long-term threat, especially for a species adapted to montane environments.
Ecotourism focused on bird-watching provides an incentive for habitat conservation in some areas of its range. Further protection of key montane ecosystems and flowering plant communities would benefit rufous-capped thornbill populations. More research focused on detecting population trends and maintaining habitat connectivity in protected areas and wildlife corridors would also be valuable conservation measures. With appropriate conservation action, the striking and energetic rufous-capped thornbill will hopefully continue thriving as an iconic part of the northern Andean avifauna.