Thursday, June 3, 2010

Flightless Birds (1)

Let's look at flightless birds.
To begin with here is some info on current flightless birds:
"Flightless birds
are birds which lack the ability to fly, relying instead on their ability to run or swim, and are thought to have evolved from their flying ancestors.[1] There are about forty species in existence today,[2] the best known being the ostrich, emu, cassowary, rhea, kiwi, and penguins. It's believed by some[citation needed] that most flightless birds evolved in the absence of predators on islands, and lost the power of flight because they had few enemies — although this is likely not the case for the ratites; the ostrich, emu and cassowary, as all have claws on their feet to use as a weapon against predators.
Two key differences between flying and flightless birds are the smaller wing bones of flightless birds and the absent (or greatly reduced) keel on their breastbone. The keel anchors muscles needed for wing movement.[2] Flightless birds also have more feathers than flying birds."

"A ratite is any of a diverse group of large, flightless birds of Gondwanan origin, most of them now extinct. Unlike other flightless birds, the ratites have no keel on their sternum - hence their name, which comes from the Latin (ratis) for raft. Without this to anchor their wing muscles, they could not fly even if they were to develop suitable wings."

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