The unique shoulder structure of hummingbirds allows the wings to beat extremely quickly in a figure-of-eight motion, enabling the birds to maintain a hovering motion whilst feeding, with up to 200 wing beats per second. Owing to this energy demanding behaviour, hummingbirds feed almost exclusively on the nectar, carbohydrate-rich sugar secretions of plants, feeding from as many as 1,000 to 2,000 flowers each day. Hummingbirds also have the highest oxygen requirement of any vertebrate, and as a result, have a breathing rate of up to 500 breaths per minute, and uniquely structured lungs. These physiological adaptations have allowed hummingbirds to occupy a vast array of habitats and altitudes throughout the Americas (6).
Little is known about the specific biology of the purple-backed sunbeam. However, it has been observed feeding on the orange-red flowers of parasitic mistletoe on Alnus trees, using its specialised bill and long, sensitive tongue to extract the nectar (5) (6). In common with most other hummingbirds, the purple-backed sunbeam is probably solitary, and aggressively territorial (6). Specimens of males with enlarged testes collected in June, suggest that the breeding season of the purple-backed sunbeam is around August to September (5). Males will mate with several females, but have no involvement in raising the offspring, with the female solely responsible for nest-building, incubation, and rearing of the chicks. The nest of a purple-backed sunbeam has never been seen, but it is most likely constructed close to a nectar source, on a branch sheltered from direct sunlight. In most hummingbirds, only two oval-shaped eggs are laid, which are incubated for around 16 to 19 days, and the chicks will remain in the nest for between 23 to 26 days after hatching (6).