The Chilean woodstar (Eulidia yarrellii) is a small hummingbird found exclusively in Chile and Argentina. With an average body length of 7-8 cm and weight of 2-3 grams, it is one of the smallest hummingbirds in the world. The male has green upperparts with a coppery-red crown and tail, and the female is duller with grayish upperparts. The Chilean woodstar inhabits temperate forests, woodlands and scrublands in the Andean foothills and valleys of central and southern Chile.
Description
The Chilean woodstar is a tiny hummingbird with a slender, slightly downcurved bill and short wings. The male has bright metallic golden-green upperparts and crown, with a brilliant coppery-red throat patch, tail and undertail coverts. The underparts are grayish white with green sides. The female is duller, with bronze-green upperparts, lighter throat and whitish underparts with grey sides. Juveniles resemble adult females but have buffy edges to the upperpart feathers.
There are two recognized subspecies. E. y. yarrellii occurs in central Chile between 32°S and 36°S. E. y. molesta is found further south from 36°S to 46°S. The latter is slightly larger with a longer bill.
Behavior and Ecology
The Chilean woodstar inhabits scrublands, open woodlands, gardens and forests in foothills and valleys. It has a predilection for Chilean pepper trees (Schinus areira) and feeds on nectar from their small white flowers. It also feeds on insects which are caught in flight.
The mating season lasts from September to January. Males display around flowering trees to defend nectar resources and attract females. Courtship displays involve hovering in front of the female and flying in U-shaped or circular patterns. The tiny cup-shaped nest is constructed from plant down bound with spider webs and lichens. It is attached to a vertical twig in a bush or tree. The female incubates the two white eggs for 15-18 days, and the chicks fledge after 20-26 days.
Conservation
The Chilean woodstar has a relatively widespread distribution across central and southern Chile and adjacent areas of southwest Argentina. The population is estimated at 10,000-100,000 individuals and is currently classified as Least Concern on the IUCN Red List. Habitat loss to agriculture, pine plantations and firewood extraction may negatively impact some populations. The species occurs in several protected areas across its range.
Unique Adaptations
The Chilean woodstar exhibits some remarkable anatomical and physiological adaptations to its small size and nectar-feeding habits:
– Extremely rapid wingbeat of around 70 beats per second, allowing great maneuverability and hovering capability. The wings move in a figure-8 pattern unlike other birds.
– A proportionally long and specialized tongue with fringed, tube-like tips to lap up nectar. The tongue darts in and out around 20 times per second.
– Tiny body feathers create excellent insulation. Nighttime hypothermia is avoided through shivering thermogenesis using specialized musculature.
– High metabolic rate with a heart rate up to 1,200 bpm. Consumes over half its weight in nectar daily and feeds every 10-15 minutes to meet energy needs.
– Enlarged hippocampus region of the brain to remember the locations of numerous scattered flower resources.
– Weighing just 2-3 grams, it is tied for the second smallest living bird species. Despite its tiny size, it migrates 500 km between breeding and wintering grounds.
The unique adaptations of the Chilean woodstar allow it to thrive on a diet of floral nectar in the moderately cold conditions of Chile and Argentina. Scientists continue to study these diminutive birds to better understand the physiological limits of birdlife. With a range limited to southern South America, conservation of its favored woodland and scrub habitat will be important for the future survival of this charming species.