Tuesday, February 21, 2012

Sea Eagles

Members of the genus Haliaeetus, sea eagles inhabit all of the continents except South America and Antarctica. Genetic studies indicate that our eight modern species are descendents of an evolutionary line that likely arose in the Oligocene, some 25-30 million years ago.

Northern sea eagles, all of which have yellow beaks, eyes and talons, are represented by the bald eagle of North America, the white-tailed eagle of Greenland, Iceland and northern Eurasia and the massive Steller's sea eagle, which inhabits the eastern coast of Siberia. The African fish eagle is found across sub-Saharan Africa while its endangered cousin, the Madagascar fish eagle, lives along the western coast of that island nation. The dull brown Pallas's fish eagle inhabits central Asia, the white-bellied sea eagle has colonized the coast of southeast Asia and Australia and Sanford's sea eagle lives in the Solomon Islands; the latter two species are thought to have diverged in the late Pleistocene.

All of these species initially evolved as coastal, fish-eating raptors, nesting on cliffs or in large trees along bays and estuaries. Several, including the bald eagle, African fish eagle and Pallas's fish eagle have since adapted to inland lakes and rivers and most of our modern species have broadened their diet to include waterfowl, sea birds, seal pups, small mammals and carrion. Though the majority are non-migratory, some northern sea eagles move southward during the winter months; it is then that bald eagles invade the U.S. Heartland, white-tailed eagles turn up along the Pakistan-India and China coasts, Pallas's fish eagles gather along the Persian Gulf and Steller's sea eagles appear on the Japanese and Korean coasts. Like all apex predators, sea eagles continue to be threatened by water pollutants that, first ingested by their prey, concentrate in the bodies of these magnificent raptors.