Purple-backed Thornbill Ramphomicron microrhynchum Scientific name definitions

The Purple-backed Thornbill boasts the smallest bill of any hummingbird. Males are a brilliant purple above with forked purplish-black tails. Females are green above and white below with green spots. These tiny hummingbirds live around the borders of humid forests, in the semi-open highlands, and in páramo. During the wet season, birds migrate to higher elevations. When feeding, Purple-backed Thornbills search for insects by gleaning and hawking, or hover at flowers. They often gather with other hummingbirds in flowering trees where they frequently perch in the treetops. During courtship displays, males dance in arc patterns back and forth in front of females and sometimes make a loud cracking sound while doing so.

8–9 cm; c. 3·5 g. Has shortest bill of any hummingbird, straight, black. Male upperparts metallic violet-purple, post­ocular spot white; gorget iridescent golden green, lower underparts bronzy-green, undertail-coverts coppery, fringed tawny; tail forked, dark purple . Female shining green above, postocular spot white; white below with large green discs, except on belly; tail less forked, dark bronzy purple, outer pairs of rectrices tipped white. Juvenile resembles adult female, young male with some purple on back. Race andicolum has gorget golden with green border, undertail-coverts more rufous; albiventre has margins of undertail-coverts lighter, female has underparts with smaller discs; bolivianum is metallic violet above, underparts dark green, undertail-coverts greyish-white with black centres.

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Editor's Note: Additional distribution information for this taxon can be found in the 'Subspecies' article above. In the future we will develop a range-wide distribution article.

Edges of humid montane forest, low shrubbery well below the tree-line in Cochabamba (Bolivia) (1 Herzog, S.K., Fjeldså, J., Kessler, M. and Balderrama, J.A. (1999). Ornithological surveys in the Cordillera Cocapata, Dpto. Cochabamba, Bolivia, a transition zone between humid and dry intermontane Andean habitats. Bull. Brit. Orn. Club. 119(3): 162–177. Close ), Polylepis forest, sub-páramo and páramo, at 1700–3600 m (2 Hennessey, A. B., and M. I. Gómez (2003). Four bird species new to Bolivia: an ornithological survey of the Yungas site Tokoaque, Madidi National Park. Cotinga 19:25–33. Close ).

Some altitudinal movements most likely.

Feeds on nectar of flowering Ericaceae, Lobeliaceae, Echeveria, Espeletia, Castilleja, Draba, Puya, Salvia and Geranium hirtum. Insects are caught in the air by hawking and taken out of Espeletia flowers. Feeds trap-lining from medium heights to canopy. Often uses holes at base of corollas made by flowerpiercers (Diglossa).

Song a continuous series of quiet scratchy notes interspersed by short buzzes or dry trills. Calls include a short dry rattle “trrr” repeated at intervals, a scratchy “krr-kit”, and a long twittering rattle.

Possibly May–Sept (Colombia), one fledgling in Dec (Ecuador). Nest described as cup-shaped, made of fine plant fibres inside, moss decorated with lichens outside, placed on horizontal branch. Clutch size two eggs; incubation 16 days, by female.

Not globally threatened. CITES II. Generally uncommon throughout its extensive range. Natural habitat, Polylepis woodland and sub-páramo, in places under severe threat of deforestation; cattle-raising leads to overgrazing with a consequent loss of plant diversity. Only recently observed for first time in depto. La Paz (Bolivia); subspecies unknown (2 Hennessey, A. B., and M. I. Gómez (2003). Four bird species new to Bolivia: an ornithological survey of the Yungas site Tokoaque, Madidi National Park. Cotinga 19:25–33. Close ). Regularly recorded in Puracé National Park (Colombia), and has also been recorded in Río Blanco Reserve, Los Nevados National Park , Chingaza National Park , Iguaque National Sanctuary and Páramo Frontino Reserve (all in Colombia), as well as Cayambe-Coca Ecological Reserve and Podocarpus National Park (3 Rasmussen, J. F., C. Rahbek, B. O. Poulsen, M. K. Poulsen, and H. Bloch (1996). Distributional records and natural history notes on threatened and little known birds of southern Ecuador. Bulletin of the British Ornithologists’ Club 116(1):26–46. Close ) (both in Ecuador) and Madidi National Park (2 Hennessey, A. B., and M. I. Gómez (2003). Four bird species new to Bolivia: an ornithological survey of the Yungas site Tokoaque, Madidi National Park. Cotinga 19:25–33. Close ) (Bolivia).