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Unlike some birds, but similar to other diurnal raptors, most hawk species are violet-sensitive but cannot perceive ultraviolet light. [11] Hawks also have relatively high visual acuity – the distance at which they can resolve an image – with red-tailed hawks reported to have 16.8 cycles per degree. [12]
This sexual difference in size is most pronounced in active species that hunt birds, such as the Accipiter hawks, in which the size difference averages 25–50%. In a majority of species, such as generalist hunters and rodent -, reptile -, fish -, and insect -hunting specialists, the dimorphism is less, usually between a 5% to 30% size difference.
The International Ornithological Committee (IOC) recognizes these 265 species of Accipitriformes distributed among four families. Among them is the family Cathartidae (New World vultures) which the American Ornithological Society (AOS), the Clements taxonomy , and BirdLife International 's Handbook of the Birds of the World place in its own ...
With a massive distributional gap consisting of most of South America, the rufous-tailed hawk is considered a separate species now, but the two hawks still form a "species pair" or superspecies, as they are clearly closely related. The rufous-tailed hawk, while comparatively little studied, is very similar to the red-tailed hawk, being about ...
Hawks, including the accipitrines, are believed to have vision several times sharper than humans, in part because of the great number of photoreceptor cells in their retinas (up to 1,000,000 per square mm, against 200,000 for humans), a very high number of nerves connecting the receptors to the brain, and an indented fovea, which magnifies the ...
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The common black-hawk is a breeding bird in the warmer parts of the Americas, from the Southwestern United States through Central America to Venezuela, Peru, Trinidad, and the Lesser Antilles. It is a mainly coastal, resident bird of mangrove swamps, estuaries and adjacent dry open woodland, though there are inland populations, including a ...
The practice of keeping and training any bird of prey is called “falconry” no matter the species of bird. Hawks are often used in the sport, as are other birds. Seen from a distance in the ...