The diminutive hummingbirds display remarkable manoeuvrability in flight, capable of hovering whilst feeding, as well as flying backwards, with up to 200 wing beats per second. Owing to this energy demanding behaviour, hummingbirds feed almost exclusively on nectar, the carbohydrate-rich sugar secretions of plants, and feed 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 uniquely structured lungs that enable them to breathe at a rate of up to 500 breaths per minute. These physiological adaptations have allowed hummingbirds to occupy a vast array of habitats and altitudes throughout the Americas (11).
Extremely active during the day (12), the ruby-throated hummingbird feeds on the nectar of orange and red flowers, with the male bird aggressively defending the flowers in its territory by spectacular chases and fights (6) (9). The ruby-throated hummingbird supplements this diet by catching insects in the air or by plucking them off spiders’ webs (6), and by taking advantage of ‘sapsucker wells’, a series of small holes in tree trunks drilled by woodpeckers from which sap oozes, attracting small insects (5).
After wintering in the southern portion of its range, the male ruby-throated hummingbird returns to its breeding grounds in late March to establish and defend a breeding territory. The females return seven to ten days later, and the males seek to attract the attention of a potential mate with elaborate courtship flights by flying upwards to 15 metres or more, and then diving at top speed, pulling up at the last moment to complete a U-shaped pattern. The sound of the male’s wings are particularly loud in courtship flight, and may be accompanied by vocalisations (5). Courtship is very brief, and once mated, the male ruby-throated hummingbird abandons the female and may begin the southward migration as early as August (13). The female then selects a nest site, often atop a small, downward-slanting branch overhanging an open area or stream (5), and constructs the nest out of spider silk, lichens and vegetation. Two eggs are usually laid and incubated for 12 to 16 days (13), with the female at the nest for 50 to 55 minutes out of each hour (5). After leaving the nest, the young ruby-throated hummingbirds are fed by the female for around 10 days (13).