They
are the smallest birds and the smallest warm-blooded animals on Earth. Most species measuring in the 7.5–13 cm (3–5 in) range. Infact, the smallest extant bird species is a hummingbird, the 5-cm Bee Hummingbird. They hover in mid-air by rapidly flapping their wings
12–80 times per second (depending on the species). They are known as
hummingbirds because of the humming sound created by their beating
wings, which flap at frequencies audible to humans
They have the fastest heart and the fastest metabolism of any
vertebrate. They are the only birds that can fly backward. And
scientists reported on Thursday that they also have a complicated assumed
evolutionary history by those evolutionary theorist
.
For such small creatures, hummingbirds have racked up an huge list of claims to fame.
Researchers constructed
the family tree of these nectar-eating birds using genetic information
from most of the world's 338 hummingbird species and their closest
relatives. They said hummingbirds can be divided into nine groups, with
differences in size, habitat, feeding strategy and body shape.
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| Picture shows how small they are |
They boast a unique set of
capabilities, said University of New Mexico ornithologist Christopher
Witt, one of the scientists in the study published in the journal
Current Biology. "They can hover stationarily or move in any direction
with precision, even in a strong wind. They also have the highest rate
of energy consumption per gram of any animal," Witt said.
Lead
author Jimmy McGuire, a biologist at the University of California at
Berkeley, said hummingbirds "have to constantly feed because they're
powering this system that has such great energy requirements."
"Many
of these hummingbirds go into torpor at night so that they don't starve
to death overnight, which is pretty cool. They're just operating on the
extremes," McGuire said.
Hummingbirds
now live only in North America, Central America, South America and the
Caribbean, but the oldest hummingbird fossils were unearthed in Europe.
That indicates that the birds once enjoyed a much larger range and
disappeared from the Old World for unknown reasons, the researchers
said.
The hummingbird
evolutionary lineage split from a related group of small birds called
swifts and treeswifts about 42 million years ago — most likely in Europe
or Asia — and by 22 million years ago the common ancestor of all
present-day hummingbirds found its way to South America, the researchers
said.
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