Olivaceous Thornbill Hummingbird Species

The Olivaceous Thornbill (Chalcostigma olivaceum) is a small hummingbird found in South America. With an average body length of 7-8 cm and weight of 3-4 grams, it is one of the smallest hummingbird species in the world. This tiny bird gets its name from its predominantly olive green plumage.

Natural Habitat and Range
The olivaceous thornbill inhabits the tropical montane cloud forests on the eastern slopes of the Andes mountains in Peru, Bolivia, and far northern Argentina at elevations between 1800-3600 meters. Its range extends from central Peru in the north to northwest Argentina in the south.

The bird’s habitat consists of dense, humid forest understory and edges with plenty of epiphytes and vines. The olivaceous thornbill prefers areas with many small flowering plants and a water source nearby. Its small size allows it to dart quickly through dense vegetation. Climate in its mountain habitat is cool and wet, with frequent mist and rain.

Identification
The olivaceous thornbill is relatively easy to identify by its distinctive olive green upperparts and off-white underparts. The crown of the head is a slightly darker olive green. The chin and throat are white, fading to pale gray across the chest and belly. A touch of cinnamon buff is sometimes visible on the sides of the neck. The tail is forked and steel blue. The long thin bill is straight and black. The wings make a high-pitched buzzing sound in flight.

Males and females look similar, but females have white spotting on the throat and chest while males have a solid white throat. Juveniles appear paler with buff spotting overall. The olivaceous thornbill exhibits no seasonal variation in its plumage. It is mostly solitary and territorial but will congregate at particularly rich nectar sources.

Diet
Like all hummingbirds, the olivaceous thornbill feeds on flower nectar and tiny insects. Its long bill allows it to access nectar deep inside long tubular flowers. Some favorite food plants include species of fuchsia, passionflower, and the giant puya plant. The bird uses its extensible tongue to lap up nectar while hovering at the flower. It also hawks small insects in flight or picks them off leaves and branches. A high metabolism requires the olivaceous thornbill to consume nectar every 10-15 minutes all day long.

Reproduction
The breeding season for the olivaceous thornbill extends from April to August in its South American range. Males perform elaborate courtship displays, flying back and forth in wide arcs with their colorful throat patch puffed out. Once paired, the female builds a delicate cup-shaped nest out of plant fibers and spider webs on a low hanging branch or tree trunk.

She lays just two tiny white eggs and incubates them alone for about 15-18 days. The chicks hatch with eyes closed and almost no feathers. Both parents feed the chicks with regurgitated insects and nectar for about 3 weeks until they fledge from the nest. The young birds reach full independence at around 6-8 weeks old. Pairs may raise two broods per season.

Threats and Conservation Status
The olivaceous thornbill’s population numbers and range are currently stable. Its remote mountain habitat protects it from most human activity. However, deforestation and climate change may impact the species in the future. Expanding agriculture and cattle ranching reduces forest area while rising temperatures dry out mountaintop cloud forests. The olivaceous thornbill is classified as Least Concern on the IUCN Red List.

Fun Facts
– The olivaceous thornbill hovers at an incredible 200 wing beats per second! This allows the bird to fly backwards and upside down while feeding.

– Its tiny nest, only about 2 inches wide, is stretched between two branches or leaves and blends into the vegetation.

– A group of hummingbirds is called a “glittering” or “shimmer”. When feeding, the olivaceous thornbill’s iridescent green back appears to shimmer in the light.

– The species name “olivaceum” is Latin for olive green, referring to the bird’s predominant body color.

– Males perform a high-speed dive display during courtship as they flash their iridescent crown and dive within inches of the female.

– Hummingbirds have remarkably short legs relative to their body size but compensating with powerfully muscled thighs for perching.

– The olivaceous thornbill’s long bill has flexible joints allowing the tips to bend up to 25 degrees in any direction to access nectar.

– This species spreads its wings out to the sides after rain to allow its feathers to dry since wet feathers are difficult to fly with.

The diminutive olivaceous thornbill thrives among the misty, moss-draped cloud forests of the South American Andes. It fills an important niche as a primary pollinator for many high altitude plants. While barely noticeable thanks to its tiny size, the olivaceous thornbill leads a fascinating life adapted for survival in the mountains. This delicate-looking but resilient species will hopefully continue brightening the tree-tops of its Andean home with its glimmering green plumage and buzzing wing-beats for a long time to come.