| Sea eagles | |
|---|---|
 | |
| Bald eagle (Haliaeetus leucocephalus) | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Accipitriformes |
| Family: | Accipitridae |
| Subfamily: | Haliaeetinae Savigny, 1809 |
| Genus | |
Asea eagle orfish eagle (also callederne orern, mostly in reference to the white-tailed eagle) is any of thebirds of prey in thesubfamilyHaliaeetinae[2] of the bird of prey familyAccipitridae. Ten extant species exist, currently described with this label.
The subfamily has a significant reach, with a scholarly article in 2005 reporting that they were "found in riverine and coastal habitat[s] throughout the world". However,Haliaeetinae inhabited areas have experienced particular threats given the context ofhuman impacts on the environment.[3]
The genusHaliaeetus was introduced in 1809 by French naturalistMarie Jules César Savigny in his chapter on birds in theDescription de l'Égypte.[4][5] The two fish eagles in the genusIchthyophaga were found to lie withinHaliaeetus in a genetic study in 2005.[3] They were then moved accordingly. They are very similar to the tropicalHaliaeetus species. A prehistoric (i.e. extinct before 1500) form from Maui in the Hawaiian Islands may represent a species or subspecies in this genus.
The relationships to other genera in the family are less clear; they have long been considered closer to the genusMilvus (kites) than to the true eagles in the genusAquila on the basis of their morphology and display behaviour;[6][7] more recent genetic evidence agrees with this, but points to their being related to the genusButeo (buzzards/hawks), as well, a relationship not previously thought close.[8]
A 2005 molecular study found that the genus isparaphyletic and subsumesIchthyophaga, the species diverging into a temperate and tropical group.[9]
Haliaeetus is possibly one of the oldest genera of living birds. Adistal lefttarsometatarsus (DPC 1652) recovered from earlyOligocenedeposits of Fayyum,Egypt (Jebel Qatrani Formation, about 33 million years ago (Mya)) is similar in general pattern and some details to that of a modern sea eagle.[10] The genus was present in the middleMiocene (12–16 Mya) with certainty.[11]
The origin of the sea eagles and fishing eagles is probably in the general area of theBay of Bengal. During theEocene/Oligocene, as theIndian subcontinent slowly collided withEurasia, this was a vast expanse of fairly shallow ocean; the initial sea eagle divergence seems to have resulted in the fourtropical (andSouthern Hemispheresubtropical) species living around theIndian Ocean today. TheCentral Asian Pallas's sea eagle's relationships to the othertaxa is more obscure; it seems closer to the threeHolarctic 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.[8]
The rate ofmolecular evolution inHaliaeetus is fairly slow, as is to be expected in long-lived birds which take years to successfully reproduce. In themtDNAcytochromeb gene, amutation 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.[8]
TheHaliaeetinae subfamily is an especially threatened collection of creatures within the broaderAccipitridae species, according to the academic journalMolecular Phylogenetics and Evolution, given the "anthropogenic factors" involved. The publication reported in 2005 that prior trends had meant that sea eagles could be "found in riverine and coastal habitat[s] throughout the world". In terms of international scientific campaigns, theConvention on International Trade in Endangered Species (CITES) protects all entities in the broader species, including sea eagles.[3]
| Image | Genus | Living Species |
|---|---|---|
.jpg) | HaliaeetusSavigny, 1809 |
|
 | Icthyophaga(Lesson, 1843) |
|
Sea eagles vary in size, fromSanford's sea eagle, averaging 2–2.7 kilograms (4.4–6.0 lb), toSteller's sea eagle, weighing up to 9 kg (20 lb).[6] At up to 6.9 kg (15 lb 3 oz), thewhite-tailed eagle is the largest eagle in Europe.Bald eagles can weigh up to 6.3 kg (13 lb 14 oz), making them the largest eagle native to North America. There are exceptional records of even heavier individuals in both the white-tailed and bald eagles, although not surpassing the largest Steller's sea eagles. Thewhite-bellied sea eagle can weigh up to 4.5 kg (9 lb 15 oz).[6] They are generally overall brown (from rich brown to dull grey-brown), often with white to the head, tail or underparts. Some of the species have an all-yellow beak as adults, which is unusual among eagles.[6]
Their diets consist mainly of fish, aquatic birds, and small mammals. Nests are typically very large and positioned in a tree, but sometimes on a cliff.[6]
The tail is entirely white in adultHaliaeetus species except for Sanford's, white-bellied, and Pallas's. Threespecies pairs exist: white-tailed and bald eagles, Sanford's and white-bellied sea eagles, and the African and Madagascar fish eagles,[8] each of these consists of a white- and a tan-headed species.
