Eagle names any big enough raptor, not one neat family branch
Genetically only Aquilinae are “true eagles,” yet English calls many large Accipitridae eagles, including the bald eagle. The word came through Old French from Latin aquila, replacing native ern. Keen eyes—wedge-tailed acuity perhaps twice a human’s—spot prey from afar.
Even small eagles such as the booted eagle carry relatively long, broad wings and heavy beaks. Nests, eyries, cling to tall trees or cliffs; many species lay two eggs, and the older chick often kills the younger while parents do not intervene. The female is larger than the male in every known species. Their sharp sight comes largely from very large pupils that limit light scattering, though like most daytime raptors they see little ultraviolet. The smallest eagle, the Great Nicobar serpent eagle, weighs about 450 grams and measures 40 centimetres; most others outsize every raptor except some vultures.
They do not live above clouds as folklore claims; they work storms and wind to glide efficiently. As avian apex predators, diets split by genus—some Haliaeetus and Icthyophaga favor fish.
Of the 68 eagle species, most live in Eurasia and Africa; just 14 live beyond those continents: nine across Central and South America, three in Australia and a mere two in North America. Functionally, an eagle is any bird of prey big enough to hunt vertebrates around half a metre long or more. The old native English word, ern, from Proto-Germanic, survives in German Aar, Dutch arend and Swedish örn, and some ornithologists still use erne for fish eagles to set them apart, though the bald and white-tailed eagles keep their common names.
Hunting styles differ by genus. Snake and serpent eagles such as Circaetus and Spilornis feed on tropical snakes in Africa and Asia, Aquila eagles dominate open country, and Haliaeetus fish eagles also rob other birds. No flying bird has been verified carrying more than one bald eagle did, a 6.8-kilogram mule deer fawn, and a martial eagle once killed a 37-kilogram duiker, seven or eight times its own weight. Unlike hawks, eagles reportedly do not glance back over their shoulders when striking.
Source: Eagle
