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Such birds may enter the water from flight, such as pelicans, gannets and tropicbirds; or they may dive from the surface of the water, such as the diving ducks, cormorants and penguins. It is theorized that they evolved from birds already adapted for swimming that were equipped with such adaptations as lobed or webbed feet for propulsion. [1]
A great cormorant swimming. Aquatic locomotion or swimming is biologically propelled motion through a liquid medium. The simplest propulsive systems are composed of cilia and flagella. Swimming has evolved a number of times in a range of organisms including arthropods, fish, molluscs, amphibians, reptiles, birds, and mammals.
[17] [18] This swim style allows the birds to swim faster and probably more efficient than if they used a regular paddling motion. The feet of grebes are quite special, resembling feathers, and the use of a lift-based propulsive mechanism suggests convergent evolution.
Many were coastal birds, strikingly resembling modern shorebirds, like Ichthyornis, or ducks, like Gansus. Some evolved as swimming hunters, like the Hesperornithiformes – a group of flightless divers resembling grebes and loons. While modern in most respects, most of these birds retained typical reptilian-like teeth and sharp claws on the manus.
There is a wide variety of webbing and lobation styles in bird feet, including birds with all digits joined in webbing, like the Brandt's cormorant and birds with lobed digits, like grebes. Palmations and lobes enable swimming or help walking on loose ground such as mud. [14]
The digestive and respiratory systems of birds are also uniquely adapted for flight. Some bird species of aquatic environments, particularly seabirds and some waterbirds, have further evolved for swimming. The study of birds is called ornithology. Birds are feathered theropod dinosaurs and constitute the only known living dinosaurs.
The shared history of birds and dinosaurs is well-established, but exactly how true birds evolved during the Mesozoic is a bit of a mystery. Adding to this conundrum are fossilized footprints of ...
The digestive and respiratory systems of birds are also uniquely adapted for flight. Some bird species of aquatic environments, particularly seabirds and some waterbirds, have further evolved for swimming. The study of birds is called ornithology. Birds are feathered theropod dinosaurs and constitute the only known living dinosaurs.