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Sea eagles
Temporal range: Eocene–Recent
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Bald Eagle
(Haliaeetus leucocephalus)
Scientific classification Red Pencil Icon
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Clade: Inopinaves
Clade: Afroaves
Superorder: Accipitrimorphae
Order: Accipitriformes
Family: Accipitridae
Subfamily: Buteoninae
Tribe: Milvini
Genus: Haliaeetus
Savigny, 1809

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[1] or the genus Ichthyophaga in the bird of prey family Accipitridae.

Description

Sea eagles vary in size, from the Sanford's Fish Eagle averaging 2–2.7 kg to the huge Steller's Sea Eagle weighing up to 9 kg.[2] 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.[2] Their diets consist mainly of fish and small mammals.

Taxonomy

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, c.33 mya) is similar in general pattern and some details to that of a modern sea-eagle.[3] The genus was present in the middle Miocene (12-16 mya) with certainty.[4]

Their closest relatives are the fishing-eagles in the genus Ichthyophaga, very similar to the tropical Haliaeetus species.[2] 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,[2][5] 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.[6]

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.[6]

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.[6]

A 2005 molecular study found that the genus is paraphyletic and subsumes Ichthyophaga, the species diverging into a temperate and tropical group.[7]

Species

There are eight living species:[2]

These birds are also included in Ichthyophaga [8]:

Three obvious species pairs exist: White-tailed and Bald Eagles, Sanford's and White-bellied Sea Eagles, and the African and Madagascar Fish Eagles.[6] Each of these consists of a white- and a tan-headed species, and the tails are entirely white in all adult Haliaeetus except Sanford's, White-bellied, and Pallas's.

Webcams

Nesting pairs of both the Bald Eagle and White-bellied Sea Eagle have been subject to live streaming web cam footage.[9][10]

References

  1. ^ Etymology: New Latin "sea-eagle", from Ancient Greek [1] Template:Polytonic (haliaetos) or Template:Polytonic (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.
  2. ^ a b c d e del Hoyo, Elliott & Sargatal 1994.
  3. ^ 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)
  4. ^ Lambrecht, K. (1933). Handbuch der Palaeornithologie. Gebrüder Bornträger, Berlin.
  5. ^ Brown, L. H, & Amadon, D. (1968). Eagles, Hawks and Falcons of the World. Country Life Books, Feltham.
  6. ^ a b c d Wink, Heidrich & Fentzloff 1996.
  7. ^ LM2005.pdf
  8. ^ John H. Boyd III (January 26, 2012). "ACCIPITRIMORPHAE: Cathartiformes, Accipitriformes". TiF Checklist. Retrieved 12-07-2020.  Check date values in: |access-date= (help)
  9. ^ AFP. "Eagle cam becomes net sensation". Sydney Morning Herald. Retrieved 5 April 2011. 
  10. ^ "EagleCam". Birds Australia website. Birds Australia. 8 February 2011. Retrieved 5 April 2011. 
Sources




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