Scientists loosely divide eagles into four groups based on their physical characteristics and behavior fish eagles, snake or serpent eagles, booted or true eagles, and harpy or buteonine eagles.
Sea or Fish Eagles
Eleven species of eagles live on the forested shores of lakes, rivers, and oceans from the Arctic Circle to the tropics, excluding South America. Their diet is heavily weighted, as one would guess from their name, in favor of fish, which may be taken alive or as carrion. However one bird sometimes placed in this group, the vulturine fish eagle, is a near-vegetarian, dining almost exclusively on the fruit of the oil palm. (This bird is also called the palm-nut vulture; it appears to be somewhere between fish eagles and vultures in both anatomy and diet.) Other members of this group include the bald eagle, the African fish eagle, and the white-tailed sea eagle.
For some fish and sea eagles, the future is uncertain. The striking Steller's sea eagle, which can weigh nearly 20 pounds (9 kg), is believed to have a world population of only about 4,200 breeding pairs. Sanford's sea eagle (Haliaeetus sanfordi) and Pallas's sea eagle are also considered to be at risk due to degradation and destruction of their habitat. The total population of the Madagascar fish eagle (Haliaeetus vociferoides), believed to be one of the world's rarest birds, is estimated at around forty pairs, which are threatened by both habitat destruction and direct persecution.
Snake or Serpent Eagles
Generally smaller than other eagles, the snake and serpent eagles hunt the savannas and forests of tropical Europe, Asia, Australia, and Africa. The most conspicuous member of this group is the flamboyantly marked bateleur. Its scarlet face and legs stand out boldly against its black, white, and chestnut plumage, and, along with its very short tail, make an adult bateleur unmistakable. The bateleur's name, given by the eighteenth century French naturalist LeVaillant, loosely translates as "tumbler" or "tightrope-walker" and undoubtedly refers to the rocking motion of its flight or the aerobatic maneuvers it sometimes performs.
This group also includes the Madagascar serpent eagle (Eutriorchis astur), which is one of the most endangered raptors in the world, For many years, it was doubted whether any survived in the wild. Finally, in 990, a dead specimen was positively identified, and in 994, a live Madagascar serpent eagle was caught. The bird's confirmed presence has added even greater urgency to the ongoing struggle to preserve Madagascar's rain forest habitat upon which so many unique animals depend.
Many of the snake and serpent eagles, particularly those of the genus Spilornis, have a very restricted range, which may be limited to one group of islands.This means that any destruction or degradation of their habitat poses a critical threat to their survival.
The booted eagles get their name because their legs are feathered right down to their ankles. This group contains the most species and numbers among them some of the most beautifully marked eagles, including the ornate hawk-eagle,the Spanish imperial eagle, and the crowned hawk-eagle. Several eagles in this group sport dashing, long crest feathers. Some booted eagles, including the martial eagle, the wedge-tailed eagle, and Verreaux's eagle, are among the largest eagles in the world; others, such as Wahlberg's eagle and Ayres's hawk-eagle, are some of the smallest. The crowned hawk-eagle has been described as one of the most powerful eagles on earth and regularly eats mammals up to twice its weight.
Two booted eagles, the golden eagle and the wedge-tailed eagle, were persecuted mercilessly in the past for their supposed habits as stock killers. Today, other members of the group are facing even greater threats. Wallace's hawk-eagle, the Philippine hawk-eagle, and the imperial eagle are considered to be highly at risk; the Javan hawk-eagle and the Spanish imperial eagle are in even more extreme peril. Deforestation of its home, combined with pressure from illegal hunting and capture for profit, has left the Javan hawk-eagle facing a bleak future. In contrast, it was reforestation, replacement of its native forest habitat with more commercially valuable trees, that was a major factor in reducing the remaining world population of Spanish imperial eagles to only about ISO pairs. Unlike the new eucalyptus and pine plantations,the original ancient oak forest was rabbit-rich and largely left alone by humans.
The vulnerability of one of the Spanish imperial eagles' last remaining refuges, Donana National Park, was evident in April 1998 when toxic mining sludge spilled into the park's Guadiamar River resulting in massive deaths of fish and invertebrates. Observers worried that the dead animals would be eaten by others in the park, including the eagles, spreading the disaster even farther. The final ecological toll will remain unknown for some time. Donana's fragile offer of sanctuary is also threatened by the power lines surrounding the park. Researchers have determined that electrocution is the main cause of mortality among the park's eagle population and that the victims are mainly juvenile females, whose survival is critical for the recovery of the species. Their larger size means that females are more likely than males to make a fatal connection,touching a live wire while perched on a metal supporting pylon. Burying transmission lines could eliminate this hazard but it is an expensive solution. Another drain on the species is the significant number of Spanish imperial eagle chicks that die each year due to Cainism. Removing chicks to foster nests is helping to reduce these losses.
At home in the tropical forests of South America, Mexico, New Guinea, and the Philippines, this group of six contains some of the world's most magnificent eagles, including the harpy eagle, the New Guinea eagle, and the Philippine eagle.
Although other eagles are almost as heavy and some have larger wingspans, the harpy eagle of South America is without doubt the world's most powerful eagle. A female harpy eagle may weigh nearly 20 pounds (9 kg). Her legs may be as big around as a child's wrist; her feet tipped with 1.5-inch-long (3.75-cm-long) talons may span 9 inches (22.5 cm). With those legs and talons, the harpy is able to snatch large arboreal prey, including sloths and howler monkeys, from the branches where they live. It required slow motion footage shot in Guyana to reveal the technique employed by the harpy to take a sloth hanging from a branch. Deftly rolling in flight to pass under the branch, the eagle grabbed the sloth, wrenched it loose, and carried it off with hardly a break in its flight. A harpy eagle swooping down at 20 miles per hour (32 kph) generates approximately 13,500 foot-pounds (18,300 Newton-meters) of energy-- that's more than twice the muzzle energy of a bullet shot from a heavy rifle. Recent research has indicated that even the harpy eagle cannot carry the biggest animals it kills back to its nest. Adult harpy eagles probably feed on a carcass for a day or two before they eventually carry the more manageable maggoty remains to their chicks.
On the other side of the world, soaring above the beech forests of lower mountain slopes, the New Guinea eagle searches for prey that may include wallabies, pig lets, and tree kangaroos. New Guinea highlanders still hunt this eagle for its wing and tail feathers, which they use in head dresses. Sadly, this practice along with the continuing destruction of its habitat means that the age-old sight of a hunting New Guinea eagle may be denied to future generations.
The stunning Philippine eagle, until recently known as the monkey-eating eagle, apparently eats more flying lemurs than monkeys. (These lemurs are 2-foot! 60-cm-long nocturnal mammals, not Madagascar primates.) There probably never were a great number of Philippine eagles; One estimate puts the maximum historical population at around six thousand individuals. As the Philippine Islands became more populated and the forests were stripped from the land, the eagle lost its home and hunting territory, and became vulnerable to shooting and trapping. Although valiant efforts to save the species continue, for the Philippine eagle, time is running out: Fewer than two hundred Philippine eagles remain, and the old-growth forest they need to survive continues to be destroyed.
Two of the best-known species of eagles, and two that show both the depredation wrought by humans on eagle populations and the extent to which repopulation efforts can succeed, are the golden and bald eagles.
Sea or Fish Eagles
Haliaeetus leucocephalus. Bald eagle.
Gypohierax angolensis.Vulturine fish eagle.
Haliaeetus albicillo.White-tailed sea eagle.
Haliaeetus leucogoster. White-bellied sea eagle.
Haliaeetus leucoryphus. Pallas's sea eagle.
Haliaeetus pelagicus. Steller's sea eagle.
Haliaeetus sanfordi. Sanford's fish eagle.
Haliaeetus vocifer.African fish eagle.
Haliaeetus vociferoides. Madagascar fish eagle.
lchthyophaga humilis. Lesser fish eagle.
lchthyophaga ichthyaetus. Gray-headed fish eagle.
Snake or Serpent Eagles
Circoetus cinerascens. Banded snake eagle.
Circaetus cinereus. Brown snake eagle.
Circaetus fasciolatus. Fasciated snake eagle.
Circaetus gallicus. Short-toed snake eagle.
In cludes C.g. beaudouini, Beaudouin's snake eagle.
Circaetus pectoralis. Black-chested snake eagle.
Dryotriorchis spectabilis. Congo serpent eagle.
Eutriorchis astur. Madagascar serpent eagle.
Spilornis cheela. Includes S.c. abbotti, Simeulue serpent eagle; S.c. asturinus, Nias serpent eagle; S.c. cheela, Crested serpent eagle; S.c. natunensis, Natuna serpent eagle; S.c. sipora, Mentawai serpent eagle.
Spilornis elgini. Andaman serpent eagle.
Spilornis holospi1us. Philippine serpent eagle. May be a race of S. cheela.
Spilornis kinabaluensis. Mountain serpent eagle.
Spilornis minimus. Small serpent eagle. Includes S.m. klossi, Nicobar serpent eagle.
Spilornis rufipectus. Sulawesi serpent eagle.
Terathopius ecaudatus. Bateleur.
True or Booted Eagles
Aquila adalberti. Spanish imperial eagle.
Aquila audax. Wedge-tailed eagle.
Aquila chrysaetos. Golden eagle.
Aquila clanga. Greater spotted eagle.
Aquila gurneyi. Gurney's eagle.
Aquila heliaca. Imperial eagle.
Aquila nipalensis. Steppe eagle.
Aquila pomarina. Lesser spotted eagle.
Aquila rapax. African tawny eagle.
Aquila verreauxii. Verreaux's eagle (black/African black eagle).
Aquila vindhiana. Eurasian tawny eagle.
Aquila wahlbergi. Wahlberg's eagle.
Hieraaetus ayresii. Ayres's hawk-eagle.
Hieraaetus fasciatus. Bonell i's eagle.
Hieraaetus kienerli. Rufous-bellied eagle.
Hieraaetus morphnoides. Little eagle.
Hieraaetus pennatus. Booted eagle.
Hieraaetus spilogaster. African hawk-eagle.
lctinaetus malayensis. Black eagle.
Lophoaetus occipitalis. Long-crested eagle.
Oroaetus isidori. Black-and-chestnut eagle.
Polemaetus bellicosus. Martial eagle.
Spizaetus africanus. Cassin's hawk-eagle.
Spizaetus alboniger. Blyth's hawk-eagle.
Spizaetus bartelsi. Javan hawk-eagle.
Spizaetus cirrhatus. Includes S.c. limnaeetus, Changeable hawk-eagle; S.c. cirrhatus, Crested hawk-eagle; S.c. floris, Sunda hawk-eagle.
Spizaetus lanceolatus. Sulawesi hawk-eagle.
Spizaetus nanus. Wallace's hawk-eagle.
Spizaetus nipalensis. Mountain hawk-eagle.
Spizaetus ornatus. Ornate hawk-eagle.
Spizaetus philippensis. Philippine hawk-eagle.
Spizaetus tyrannus. Black hawk-eagle.
Spizastur melanoleucus. Black-and-white hawk- eagle.
Stephanoaetus caronatus. Crowned hawk-eagle.
Harpy or Buteonine Eagles
Harpia harpyja. Harpy eagle.
Harpyhaliaetus caranatus. Crowned eagle.
Harpyhaliaetus solitarius. Solitary eagle.
Harpyopsis novaeguineae. New Guinea eagle.
Morphnus guianensis. Crested eagle.
Pithecophaga jefferyi. Philippine eagle.
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The information on this page is from "Eagles Masters of the Sky" by Rebecca L. Grambo - Editor © 1997 Published by Voyageur Press, Inc., and is being used with permission from Rebecca L. Grambo.