Wednesday, 5 October 2011

American Crow

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The American crow is the “default” crow across most of North America. It overlaps broadly with the common raven, and to a lesser extent with the Chihuahuan raven, fish crow, and northwestern crow. Study of vocalizations, bill structure and size, tail shape, and overall structure of this species will greatly aid in the identification of other crows and ravens. Regional variation in size of the American crow poses challenges, particularly in the northwest. Polytypic. Length 17.5" (45 cm).

Seabird

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Seabird
Seabirds (also known as marine birds) are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations. The first seabirds evolved in the Cretaceous period, and modern seabird families emerged in the Paleogene.

In general, seabirds live longer, breed later and have fewer young than other birds do, but they invest a great deal of time in their young. Most species nest in colonies, which can vary in size from a few dozen birds to millions. Many species are famous for undertaking long annual migrations, crossing the equator or circumnavigating the Earth in some cases. They feed both at the ocean's surface and below it, and even feed on each other. Seabirds can be highly pelagic, coastal, or in some cases spend a part of the year away from the sea entirely.

Seabirds and humans have a long history together: they have provided food to hunters, guided fishermen to fishing stocks and led sailors to land. Many species are currently threatened by human activities, and conservation efforts are under way.

How Eagle Prey

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Tuesday, 4 October 2011

Eagle

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Eagles are members of the bird family Accipitridae, and belong to several genera which are not necessarily closely related to each other. Most of the more than 60 species occur in Eurasia and Africa.[1] Outside this area, just two species (the Bald and Golden Eagles) can be found in the United States and Canada, nine more in Central and South America, and three in Australia.
Description

Eagles differ from many other birds of prey[which?] mainly by their larger size, more powerful build, and heavier head and beak. Even the smallest eagles, like the Booted Eagle (which is comparable in size to a Common Buzzard or Red-tailed Hawk), have relatively longer and more evenly broad wings, and more direct, faster flight. Most eagles are larger than any other raptors apart from the vultures. Species named as eagles range in size from the South Nicobar Serpent Eagle, at 500 g (1.1 lb) and 40 cm (16 in), to the 6.7 kg (14.7 lbs) Steller's Sea Eagle and the 100 cm (39 in) Philippine Eagle. Like all birds of prey, eagles have very large hooked beaks for tearing flesh from their prey, strong muscular legs, and powerful talons. The beak is typically heavier than most other birds of prey. They also have extremely keen eyesight which enables them to spot potential prey from a very long distance.[2] This keen eyesight is primarily contributed by their extremely large pupils which ensure minimal diffraction (scattering) of the incoming light.

Eagles build their nests, called eyries, in tall trees or on high cliffs. Many species lay two eggs, but the older, larger chick frequently kills its younger sibling once it has hatched. The dominant chick tends to be the female, as they are bigger than the male. The parents take no action to stop the killing.[3][4]