Eagles of the World
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.