|
A sea eagle (also called erne or ern, mostly in reference to the white-tailed eagle) is any of the birds of prey in the genus ''Haliaeetus''〔Etymology: New Latin "sea eagle", from Ancient Greek () (''haliaetos'') or (''haliaietos'', poetic (e.g. Homeric) variant), "sea eagle, osprey" (''hali'', "at sea" (dative case), + ''aetos'', "eagle"). The two variant Greek forms lie behind the equally correct Latinizations ''haliaetus'' (as in ''Pandion haliaetus'') and ''haliaeetus''.〕 in the bird of prey family Accipitridae. Sea eagles vary in size, from Sanford's sea eagle, averaging 2.0–2.7 kg, to the huge Steller's sea eagle, weighing up to 9 kg. At up to 6.9 kg, the white-tailed eagle is the largest eagle in Europe. Bald eagles can weigh up to 6.3 kg, making them the largest eagle native to North America. The white-bellied sea eagle can weigh up to 3.4 kg. Their diets consist mainly of fish and small mammals. The eight living species are: * White-bellied sea eagle (''H. leucogaster'') * Sanford's sea eagle (''H. sanfordi'') * African fish eagle (''H. vocifer'') * Malagasy fish eagle (''H. vociferoides'') * Pallas's fish eagle (''H. leucoryphus'') * White-tailed eagle (''H. albicilla'') * Bald eagle (''H. leucocephalus'') * Steller's sea eagle (''H. pelagicus'') Their tails are entirely white in all adult ''Haliaeetus'' species except Sanford's, white-bellied, and Pallas's. Three species pairs exist: white-tailed and bald eagles, Sanford's and white-bellied sea eagles, and the African and Madagascar fish eagles, each of these consists of a white- and a tan-headed species. ''Haliaeetus'' is possibly one of the oldest genera of living birds. A distal left tarsometatarsus (DPC 1652) recovered from early Oligocene deposits of Fayyum, Egypt (Jebel Qatrani Formation, about 33 Mya) is similar in general pattern and some details to that of a modern sea eagle.〔Rasmussen, D., Tab, O., Storrs, L., & Simons, E. L. (1987). Fossil Birds from the Oligocene Jebel Qatrani Formation, Fayum Province, Egypt. ''Smithsonian Contributions to Paleobiology'' 62: 1-20. (PDF Fulltext ) (file size 8.1 MB)〕 The genus was present in the middle Miocene (12-16 Mya) with certainty.〔Lambrecht, K. (1933). ''Handbuch der Palaeornithologie''. Gebrüder Bornträger, Berlin.〕 Their closest relatives are the fishing eagles in the genus ''Ichthyophaga'', very similar to the tropical ''Haliaeetus'' species. The relationships to other genera in the family are less clear; they have long been considered closer to the genus ''Milvus'' (kites) than to the true eagles in the genus ''Aquila'' on the basis of their morphology and display behaviour,〔Brown, L. H, & Amadon, D. (1968). ''Eagles, Hawks and Falcons of the World''. Country Life Books, Feltham.〕 more recent genetic evidence agrees with this, but points to them being related to the genus ''Buteo'' (buzzards), as well, a relationship not previously thought close. The origin of the sea eagles and fishing eagles is probably in the general area of the Bay of Bengal. During the Eocene/Oligocene, as the Indian subcontinent slowly collided with Eurasia, this was a vast expanse of fairly shallow ocean; the initial sea eagle divergence seems to have resulted in the four tropical (and Southern Hemisphere subtropical) species found around the Indian Ocean today. The Central Asian Pallas's sea eagle's relationships to the other taxa is more obscure; it seems closer to the three Holarctic species which evolved later and may be an early offshoot of this northward expansion; it does not have the hefty yellow bill of the northern forms, retaining a smaller, darker beak like the tropical species. The rate of molecular evolution in ''Haliaeetus'' is fairly slow, as is to be expected in long-lived birds which take years to successfully reproduce. In the mtDNA cytochrome ''b'' gene, a mutation rate of 0.5–0.7% per million years (if assuming an Early Miocene divergence) or maybe as little as 0.25–0.3% per million years (for a Late Eocene divergence) has been shown. A 2005 molecular study found that the genus is paraphyletic and subsumes ''Ichthyophaga'', the species diverging into a temperate and tropical group.〔(LM2005.pdf )〕 ==Webcams== Nesting pairs of both the bald eagle and white-bellied sea eagle have been subject to live streaming webcam footage. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sea eagle」の詳細全文を読む スポンサード リンク
|