|Photographed in the Kruger National Park, South Africa|
Wahlberg's eagle (Hieraaetus wahlbergi) is a bird of prey that is native to sub-Saharan Africa, where it is a seasonal migrant in the woodlands and savannas. It is named after the Swedish naturalist Johan August Wahlberg. Like all eagles, it belongs to the family Accipitridae.
Wahlberg's eagle is a medium-sized raptor, and the sexes are similar. It is about 53–61 cm (21–24 in) in length with a wingspan of 130–146 cm (51–57 in) and a body mass of 437–845 g (15.4–29.8 oz) for males and 670–1,400 g (24–49 oz) for females on average. The head has a small crest, and the legs are yellow. The plumage tone is variable but may be dark brown except for dark-streaked grey undersides to the flight feathers, and a barred grey undertail. Light and dark plumage phases occur. A pale variant may be much lighter brown with whitish, rather than grey undertail and flight feather undersides. The pale variant is much less common than the darker variant.
Distribution and habitat
Wahlberg's eagle is distributed from central Chad to the north-east coast of South Africa. Its western boundary is thought to be Cameroon, although it most commonly occurs further east across the continent. Within this large range, it usually remains between sea-level and 1,800 m (5,900 ft), but has also been documented at an altitude of 2,800 m (9,200 ft) in Ethiopia.
Wahlberg's eagles cover large distances in short periods. In 1994, a female Wahlberg's eagle was tracked over a period of 9 months, during which it covered over 8,800 km (5,500 mi) from northern Namibia to Chad and back; its range between breeding in the south and non-breeding areas in the north was 3,520 km (2,190 mi), and it travelled over 700 km (430 mi) due north in just five days after leaving its breeding grounds.
Behaviour and ecology
Wahlberg's eagle mainly hunts birds (including other raptors such as the Gabar goshawk and Barn owl), although it also feeds on reptiles (various lizards and snakes) and a few small mammals (Tree squirrels, Mongooses, Hares). It has also been recorded eating various Invertebrates such as termites, grasshoppers and beetles.
Wahlberg's eagle breeds mainly in southern Africa during the October to February period. It builds a stick nest in the fork of a tree or the crown of a palm tree. Wahlberg's eagles are monogamous and form long-term pair bonds. They are well known for complex and spectacular aerial courtship displays. They are very territorial and solitary nesters. The nest is often reused by the same pair through multiple years. Their breeding season occurs during the wet season of northern South Africa from October to February as food is more readily available. The female feeds the chicks with food provided by the male eagle. Reductions in reproductive output were observed in the 1990s, which were thought to be related to increased population density in Wahlberg's eagles; breeding success was highly density dependant, and resource availability did not play a part in this phenomenon.
Studies of marker gene sequences (published 2004–2005) found Wahlberg's eagle belonged to a clade containing Hieraaetus pennatus, H. morphnoides, H. ayeresii, and H. (m.) weiskei. Since then, many taxonomic checklists changed from Aquila wahlbergi to Hieraaetus wahlbergi. However, the African Bird Club (as of the 2012 checklist) and the Second Southern African Bird Atlas Project (as of 2014) continue to keep Aquila wahlbergi separate from the Hieraaetus species.
- BirdLife International (2016). "Hieraaetus wahlbergi". IUCN Red List of Threatened Species. 2016: e.T22696072A93543119. doi:10.2305/IUCN.UK.2016-3.RLTS.T22696072A93543119.en. Retrieved 19 November 2021.
- "Wahlberg's Eagle". www.oiseaux-birds.com. Retrieved 2022-07-19.
- Mayburg, B.U. (1995). "Year-round movements of a Wahlberg's eagle Aquila wahlbergi tracked by satellite". Ostrich. 66 (4).
- Peter, S. (1991). Birds of Southern Africa. Central News Agency. ISBN 0-86283-855-X. OCLC 51358656.
- "Aquila wahlbergi (Wahlberg's eagle)". www.biodiversityexplorer.info. Retrieved 2022-07-19.
- Simmons, R. E. (1993). "Effects of supplementary food on density-reduced breeding in an African eagle: adaptive restraint or ecological constraint?". Ibis. 135 (4): 394–402. doi:10.1111/j.1474-919X.1993.tb02111.x.
- Helbig, Andreas J.; Kocum, Annett; Seibold, Ingrid; Braun, Michael J. (2004). "A multi-gene phylogeny of aquiline eagles (Aves: Accipitriformes) reveals extensive paraphyly at the genus level". Molecular Phylogenetics and Evolution. 35 (1): 147–164. doi:10.1016/j.ympev.2004.10.003. PMID 15737588.
Wahlberg's Eagle H. wahlbergi, formerly placed in Aquila, is part of a clade including three small Hieraaetus species (pennatus, ayresii, and morphnoides)
- Wink, Michael; Sauer-Gürth, Heidi (2004). "Phylogenetic relationships in diurnal raptors based on nucleotide sequences of mitochondrial and nuclear marker genes". In Chancellor, R. D.; Meyburg, B.-U. (eds.). Raptors Worldwide. WWGBP/MME. pp. 483–498. PDF alternate location
- Lerner, Heather R. L.; Mindell, David P. (2005). "Phylogeny of eagles, Old World vultures, and other Accipitridae based on nuclear and mitochondrial DNA". Molecular Phylogenetics and Evolution. 37 (2): 327–346. doi:10.1016/j.ympev.2005.04.010. PMID 15925523. PDF alternate location
- Le Page, Denis. "Wahlberg's eagle". Avibase Taxonomic Concepts. Retrieved 5 October 2014.
Note that, in addition to Clements and Birdlife International, Avibase lists the following authorities as using H. wahlbergi:
- Commission internationale pour les noms français des oiseaux (1993, révision 2009)
- Howard & Moore (2nd and 3rd editions)
- IOC World Bird Names (from version 2.0)
- The Clements Checklist team (23 December 2009). "Updates & Corrections – December 2009". The Cornell Lab of Ornithology. Retrieved 21 June 2014.
Pages 47-48, Wahlberg's Eagle Aquila wahlbergi, Booted Eagle Aquila pennata, Little Eagle Aquila morphnoides, Ayres's Hawk-Eagle Aquila ayresii. All of these eagles belong in the genus Hieraaetus
- BirdLife Taxonomic Checklists listed A. wahlbergi in versions 0 (2007) through 6.1 (February 2014). From version 7 (July 2014), their taxonomy of non-passerines is based on del Hoyo et al. 2014, and Wahlberg's eagle is listed as H. wahlbergi. All versions available via "Taxonomy". BirdLife International. Archived from the original on 2014-09-24. Retrieved 5 October 2014.
- Boyd, John. "Accipitrimorphae". Taxonomy in Flux Checklist. Retrieved 5 October 2014.
- African Bird Club continues to use A. wahlbergi, as does SABAP2. However, BirdLife South Africa (formerly South African Ornithological Society) uses H. wahlbergi in its 2014 checklist. Note that ABC and SABAP2 still recognize genus Hieraaetus, they just don't include Wahlberg's eagle in it. This is different from some other authors who merged all of Hieraaetus into Aquila. See the Hieraaetus article for further discussion of this merger.
- Wahlberg's eagle - Species text in The Atlas of Southern African Birds