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Rufous Tailed Hummingbird
The rufous-tailed hummingbird (Amazilia tzacatl) is a medium-sized perky, active and aggressive species that occurs in a variety of habitats. It prefers open scrubby areas, gardens and plantations. It regularly visits nectar-feeders.
It forages for nectar on many types of flowering plants; Hamelia, Heliconia and Cephaelis. Males vigorously defend foraging sites. Studies by University of Missouri researchers show that aggression by males tapers off if intruders vastly outsize the combative individual. Smaller intruders are vigorously attacked. Studies show that if males of this species perceive the local food resources are extensive; their combative enthousiasm becomes more acute.
Males are extraordinarily vocal, some singing all day virtually non-stop. The call is shrill, raspy and often metallic, sometimes repeated in bursts.
Up to 200 wing beats per second!
Research in Costa Rica shows that these hummingbirds often become entangled in spider webs (sometimes fatally). They are apparently drawn to the webs by entrapped insects upon which they sometimes feed. This species also sometimes collides with windows.
Researchers confirm the rufous-tailed hummingbird can vary the frequency of its wing beats according to the type of flower upon which it is foraging. Hovering above large-diameter flowers takes much more energy because wing beats increase to compensate for reduced wing beat amplitude. About 10 percent less energy is needed for foraging on small-diameter flowers. The normal wing beat rate is about 70 beats per second, with beat of up to 200 per second during aerial displays. Wing muscles make up about 25 percent of the total body weight.
This species occurs over a large area, from Mexico to Colombia. It is common throughout its range and is the most abundant hummingbird in Costa Rica.
Rufous-tailed hummingbirds are just over four inches in total length. The female is solely responsible for rearing offspring. The nest is a tiny cup, usually located on a narrow horizontal branch. Two white eggs are incubated for about 16 days. The fledging period is 20-26 days.
This species occurs regularly at Selva Verde and in the surrounding countryside. It is a tame species, easily approached, often frequenting the gardens near the cabins.
This hummingbird has considerable geographic variation resulting in at least 5 different subspecies. More are likely to be discovered, researchers say, owing to the diversity of habitats where the bird is found. So far, the subspecies are; A.t. tzacatl, A.t. handleyi, A.t. jucunda, A.t. fuscicaudata and A.t. brehmi.
- Robert Alison, PhD
Robert is an avian ecologist and ornithologist based in Victoria, British Columbia. He is a frequent contributor to Field Notes.
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