The little woodstar (Chaetocercus bombus) is a tiny hummingbird found in western South America. With an average body length of just 5-6 cm (2-2.5 in) and weight of 2-3 grams, it is one of the smallest hummingbird species in the world. Despite its diminutive size, the little woodstar exhibits remarkable adaptations that enable it to survive and thrive in its environment.
Range and Habitat
The little woodstar has a broad range extending from central Peru south through Bolivia to northern Chile and Argentina. It inhabits dry forests, scrublands, and mountain valleys at elevations between 500-4000 meters.
Within its range, the little woodstar shows a strong preference for arid environments. It is most abundant in dry intermontane valleys dominated by flowering cacti and thorny trees. TheFragmented woodlands, scrublands, and cactus forests likely provide more favorable foraging conditions for the nectar-feeding little woodstar compared to wetter habitats.
Description
The little woodstar exhibits sexual dimorphism in its plumage. Adult males have a metallic green crown and throat, with a blackish mask across the face. The upperparts and tail are golden brown. The underparts are white with green spotting on the sides. Females lack the bright crown patch and have whitish edges on the tail feathers. Both sexes have a very short black bill adapted for accessing nectar from flowers.
Like all hummingbirds, the little woodstar has unique anatomical adaptations related to flight. The wings beat 55 times per second, enabling the bird to hover in place or fly backwards. Extremely light, porous bones account for just 4% of their body weight. Outsized flight muscles make up 25% of their weight. These adaptations allow the little woodstar to exhibit remarkable aerial agility and access flowers inconspicuous to other animals.
Diet and Foraging
The little woodstar subsists almost entirely on nectar from flowers. Its short bill is specialized for lapping up nectar. As the bird feeds, pollen sticks to its head and bill, allowing it to play an important role as a pollinator for many plant species.
This tiny hummingbird has a remarkably fast metabolism. It must consume half its body weight in nectar daily, visiting hundreds or even over a thousand flowers per day. The main food plants include various cacti and flowering trees and shrubs adapted to arid environments, such as Puya bromeliads, morning glories, and coral trees.
Agile flight allows the little woodstar to exploit food resources unavailable to many larger animals. It prefers flowers with minimal ornamentation that face upwards, allowing easy access while hovering. Nectar robbery by piercing the base of the corolla is also common in this species.
To meet its extreme metabolic demands, the little woodstar feeds almost continuously throughout the day, with feeding bouts lasting just a few seconds at each flower. It aggressively defends particularly productive feeding patches against intrusions by other hummingbirds through aerial chases.
Unique Adaptations
Several unique adaptations of the little woodstar aid its survival in harsh desert environments. It exhibits a hibernation-like torpor to conserve energy on cool nights. Body temperature drops by up to 30 ̊C and the bird enters a dormant state. This adaptation allows it to minimize energy use when food is unavailable.
Water is scarce in their arid habitats. The little woodstar obtains most of its water needs from the nectar it consumes. Its kidneys are extremely efficient at minimizing water loss through excretion.
Breeding Biology
The breeding season of the little woodstar coincides with peaks in flower and nectar availability from March to June. Males establish breeding territories with plentiful flower resources that they vigorously advertise and defend from other males through complex aerial displays.
Females build a tiny cup nest on the underside of overhanging cliffs or rocks, under the eaves of buildings, or in crevices using spider webs and lichens. The female lays just two tiny white eggs. She alone cares for the chicks, feeding them with nectar and small insects. The chicks fledge in about 3 weeks.
Status and Threats
The little woodstar remains fairly common throughout its range and is evaluated as a species of least concern by the IUCN. However, habitat loss is occurring in some regions due to development and agriculture. The arid ecosystems favored by the little woodstar are also highly vulnerable to climate change, which may shift suitable habitat and food resources.
Conclusion
The petite little woodstar exhibits many unique adaptations for life in the arid environments of South America. Its tiny size, extreme metabolism, and hover-feeding behavior allow it to exploit floral nectar unavailable to most other birds and animals. Despite its small stature, this energetic hummingbird plays an integral role as a pollinator in fragile desert ecosystems. Maintaining intact arid habitats will be crucial for ensuring the future of this diminutive yet important resident of South American deserts.