The genus Hieraaetus, sometimes known as small eagles or hawk-eagles, denotes a group of smallish eagles usually placed in the accipitrid subfamilies Buteoninae Digitized copy or Aquilinae.
They are generally medium-sized birds of prey inhabiting Europe, Asia, Africa, New Guinea and Australia. However, a recently extinct species, the New Zealand Haast's eagle, was the largest eagle ever known, weighing up to , with a wingspan.
Taxonomy and species The genus Hieraaetus was introduced in 1844 by the German naturalist Johann Jakob Kaup with the booted eagle as the type species. The name combines the Ancient Greek hierax meaning "hawk" with aetos meaning "eagle".
Molecular genetic research has found Hieraaetus to be polyphyletic with Aquila.
Hieraaetus kienerii was found to be most distinct, proof Jan Ove Gjershaug (2006) Taxonomy and conservation status of hawk-eagles (genus Nisaetus) in South-East Asia. Thesis. Norwegian University of Science and Technology Fulltext and has been assigned to a separate genus, Lophotriorchis.PDF alternate location "Despite the fact that its sister group has not been identified so far, it is advisable to separate it from the genus Hieraaetus and treat it as a different genus. ... Therefore, we propose to give the monotypic species Hieraaetus kienerii the resurrected name Lophotriorchis Sharpe, 1874."
After DNA sequences from remains of the extinct giant Haast's eagle were found to be similar to those of the little eagle, it has been reclassified from Harpagornis moorei to the genus Hieraeetus.
The British Ornithological Union moved Bonelli's and booted eagles to Aquila in 2005, but was silent on the position of the non-European Ayres', little, and pygmy eagles.Recommended in Also summarized in
This could create a taxonomic problem: the booted eagle is the type species of Hieraaetus, moving it would make that name a junior synonym of Aquila. Consequently, should any other hawk-eagles be retained as a distinct group, they would need to get a different genus name. As of 2014, the BOU lists the booted eagle on their Category D and E lists as H. pennatus, not A. pennata.
Christidis and Boles (2008) used an alternative approach. Accepting that both Aquila and Hieraaetus are polyphyletic, they moved spilogaster and fasciatus to the genus Aquila and retained the other former Hieraaetus group along with morphnoides and Aquila wahlbergi within the new delimitation of Hieraaetus.Les Christidis & Walter E Boles (2008) Systematics and Taxonomy of Australian Birds. CSIRO publishing.
Sometimes the entire genus was merged into Aquila. This was the approach taken with The Clements Checklist between 2001 and 2009: starting in the 2001 revisions to the 5th edition, (See also similar pages for the other species.) and retained in the printed 6th edition of 2007.
The Clements Checklist, in its 2009 revisions, followed the same approach as Christidis & Boles, moving Aquila wahlbergi into Hieraaetus; restoring the booted, little and Ayres' eagles back to Hieraaetus.
The pygmy eagle, or New Guinea hawk-eagle, H. morphnoides weiskei was formerly considered a subspecies of the little eagle H. morphnoides; it has been recognized as a separate species by some authorities.
A more recent molecular study by Catanach et al. (2024), which included ultra-conserved genetic elements, supported the continued separation of Hieraaetus from Aquila, with H. wahlbergii in the former and A. spilogaster plus A. fasciata in the latter. It found H. wahlbergii diverged earliest, followed by Hieraaetus ayresii, then the remaining four species more tightly grouped.
The genus contains five species.
Image Scientific name Common name DistributionHieraaetus wahlbergiWahlberg's eagleAfrica Hieraaetus ayresiiAyres's hawk-eagle Africa Hieraaetus pennatusBooted eagle Eurasia and AfricaHieraaetus weiskeiPygmy eagleNew GuineaHieraaetus morphnoidesLittle eagleAustralia
Extinct species Image Scientific name Common name Distribution †Hieraaetus moorei Haast's eagle New Zealand, extinct
Former species Image Scientific name Common name DistributionAquila spilogaster(formerly H. fasciatus spilogasteror A. fasciatus spilogaster)African hawk-eagle Sub-Saharan Africaexcluding rainforestsAquila fasciata(formerly H. fasciatus)Bonelli's eagleMediterranean and southern AsiaLophotriorchis kienerii(formerly H. kienerii)Rufous-bellied eagleAsia Some authorities retain Bonelli's eagle and the African hawk-eagle in Hieraaetus. Also, some retain Wahlberg's eagle in Aquila, whilst still recognizing Hieraaetus as a separate genus.
Notes
References
Helbig AJ, Kocum A, Seibold I & Braun MJ (2005) A multi-gene phylogeny of aquiline eagles (Aves: Accipitriformes) reveals extensive paraphyly at the genus level. Molecular Phylogenetics and Evolution 35(1):147-164 PDF