Open Access
How to translate text using browser tools
1 July 2007 Cassin's Hawk-Eagle Spizaetus africanus in Ndundulu Forest: a First Record for Tanzania, with Biogeographical Implications
Trevor Jones
Author Affiliations +

A single adult Cassin's hawk-eagle Spizaetus africanus was sighted on five occasions over three years in a highland forest in the Udzungwa Mountains, the first ever record of this species in Tanzania. This discovery has potentially significant biogeographical implications, strengthening ancient links between the forests of the Udzungwa Mountains and the Guineo-Congolian forests of central Africa.

Cassin's hawk-eagles are the only African representative of the tropical genus Spizaetus Vieillot, 1816, a group of small to medium sized eagles with short, rounded wings and long tails (Brown et al., 1982; Ferguson-Lees & Christie, 2001; though for current taxonomic debate based on recent molecular analyses see Helbig et al., 2005; Lerner & Mindell, 2005; Haring et al., 2007). Spizaetus africanus Cassin, 1865 is a forest eagle with a black-and-white appearance (wing length, male 330–341 mm, female 381 mm; tail length, male 211–234 mm, female 266 mm) (Ferguson-Lees & Christie, 2001). The adult is mainly white below with black patches on the side of the breast, and blackish axillaries and underwing-coverts. Above it is mainly black, with black-tipped primaries. The tail is banded dark and light brown; cere and feet are pale yellow. It is known to be resident in dense tropical forests across Equatorial Africa, from Togo east to Gabon, Cameroon and the Democratic Republic of Congo. The easternmost known site for this species is the Mabira Forest Reserve of central Uganda (Fishpool & Evans, 2001), though a dead juvenile was found on Mount Elgon in western Kenya in 1926 (Clark & Edelstam, 2001) (figure 1).

Figure 1.

Map showing the currently known distribution of Cassin's hawk-eagle Spizaetus africanus in East Africa, including Ndundulu Forest, Tanzania. Mount Elgon, Kenya, from where a juvenile specimen was collected in 1926, is also shown.


A single adult Cassin's hawk-eagle was observed on five occasions between September 2004 and November 2007 (11 September 2004, 13 September 2004, 19 February 2006, 29 August 2006, 2 November 2007) in Ndundulu Forest (7°45′S, 36°30′E; 1300–2000 m) in the Udzungwa Mountains of southern Tanzania (figure 1). The plumage pattern and feathered tarsi of the observed and photographed bird (figure 2) are diagnostic. The amount of white on the underparts is consistent with Cassin's hawk-eagle and distinguishes it from African hawk-eagle Aquila spilogaster Bonaparte, 1850 (Helbig et al., 2005; formerly Hieraaetus spilogaster: Brown et al., 1982; Ferguson-Lees & Christie, 2001) and Ayres' eagle Hieraaetus ayresii Gurney, 1862. The white feathered tarsi, and black underwing coverts observed in flight, distinguish it from the Black sparrowhawk Accipiter melanoleucus Smith, 1830. Colour and length of the tail distinguish it from the Augur buzzard Buteo augur Rüppell, 1836. Single birds were spotted on two occasions sitting in the tall upper canopy of the forest (which reaches over 50 m in height), and on three occasions soaring in circles low over the forest canopy. On two occasions a bird was heard calling while in flight, a short high-pitched call repeated several times, which was later recorded and compared with and noted to sound identical to an audio recording of Cassin's hawk-eagle. It is not possible to confirm whether all encounters have been with the same or different individuals.

Figure 2.

An adult Cassin's hawk-eagle Spizaetus africanus, photographed in Ndundulu Forest, Tanzania, August 2006. Photograph by Anthony Jarrett.


Ndundulu and the contiguous Luhomero Forest (to 2500 m) cover a total area of 250 km2 comprising closed canopy forest with a few open clearings, and is one of the richest and most biodiverse of all forests in Tanzania (Dinesen et al., 2001; Burgess et al., 2007). As an indication of its extraordinary richness across all taxa, it is home to 22 restricted-range bird species (Marshall et al., 2001; T. Jones, unpubl. data) and at least three restricted-range primate species, including the recently discovered kipunji Rungwecebus kipunji Davenport et al., 2006 (Jones et al., 2005; Davenport et al., 2006). There have also been discoveries in recent years of a new genus and species of bird (Dinesen et al., 1994), a new species of giant sengi or elephant shrew (Rovero & Rathbun, 2006; Rovero et al., in press), and a new species of shrew (Stanley et al., 2005). The discovery of Cassin's hawk-eagle here further reinforces the perception of Ndundulu as an outstanding refuge for relic faunal populations.

All five sightings to date have been made within an area of 7 km2 in southern Ndundulu, although several weeks of survey effort were completed during 2005–2006 in other parts of this forest (Jones, 2006). However, these surveys were primarily focused on primates and the apparent tendency of these birds to spend most of the time in or above the forest canopy makes them very difficult to detect (Friedmann & Williams, 1970). A failure of previous surveys to detect this species does not prove that it was absent (Dinesen et al., 1993; Hunter et al., 1996; Butynski & Ehardt, 2003). Moreover, there are large areas of the surrounding forest which have not yet been surveyed. The minimum 250 km2 of available potential habitat in Ndundulu/Luhomero raises the possibility of a small viable population of resident Cassin's hawk-eagles, and it is not inconceivable that they could also have gone undetected by researchers in neighbouring forests such as Nyumbanitu (49 km2) (e.g. Dinesen et al., 1993, 2001; Marshall et al., 2001). It is now important that further investigations focused on this species are carried out to determine distribution, abundance and breeding status in the Udzungwa Mountains.

The nearest reported site of Cassin's hawk-eagle to Ndundulu is in Mabira Forest Reserve, south-central Uganda, 900 km away (figure 1). The discovery of this bird in Ndundulu has interesting implications for the debate over the presence and timing of an ancient continuous forest between the Udzungwa Mountains (and other forested highlands of Tanzania) and the Guineo-Congolian forests of central and western Africa (Axelrod & Raven, 1978; White, 1981; Lovett, 1993a; Burgess et al., 2007). Although the Tanzanian highland forests have been isolated for several million years, recent discoveries of organisms endemic to these mountains, but having Guineo-Congolian affinities, have argued for a more contiguous historical distribution of species, maybe as recently as 10 million years ago. For example, the Udzungwa-endemic gecko Urocotyledon rasmusseni Bauer & Menegon, 2006 is more closely related to U. weileri Müller, 1909 of West Africa than to its Tanzanian relative U. wolterstorffi Tornier, 1900 (Bauer & Menegon, 2006). There are butterflies (De Jong & Congdon, 1993), reptiles (Howell, 1993) and trees (Lovett, 1993b) in the Udzungwas with close Guineo-Congolian affinities, and the recent discovery of the shrew Congosorex phillipsorum in Ndundulu marked the first known record of a mammalian genus with disjunct species in these mountains and in central Africa (Stanley et al., 2005). Among birds, molecular analyses of some isolated eastern Tanzanian montane subspecies have shown them to be divergent from relatives in the Central Congolian forests (Roy, 1997; Roy et al., 1997; Beresford, 2003). Although birds are generally more mobile dispersers across different habitats than other vertebrates, the unexpected presence of the forest-dependent Cassin's hawk-eagle in Ndundulu, if it is indeed indicative of a relic population, lends further support to the theory of more contiguous forest between the Congo Basin and southern Tanzania than is found today.


I am grateful to Simon Thomsett, Munir Virani, Simon Mann, Neil Baker and other contributors to the Tanzania Birds email group for assisting with species identification; to Pete Leonard for providing an audio recording of Cassin's hawk-eagle; and to Bill Stanley and Rebecca Banasiak (Field Museum of Natural History, Chicago) for helping with the map. Thanks to my field assistant Athumani Mndeme and to many people from Udekwa who have helped in the forest. Special thanks to Anthony Jarrett for the photograph. All observations were made during fieldwork funded by the Critical Ecosystem Partnership Fund, Wildlife Conservation Society, Fauna and Flora International, and the Primate Society of Great Britain. Research permission was granted by the Tanzania Wildlife Research Institute, the Commission for Science and Technology, and the Tanzania Forestry and Beekeeping Division. The manuscript was improved by comments from Simon Thomsett and two anonymous reviewers.



D. I. Axelrod and P. H. Raven . 1978. Late Cretaceous and Tertiary vegetation history of Africa. In M. J. A. Werger , editor. (ed.). Biogeography and Ecology of Southern Africa Junk. The Hague. Pp. 77–130. Google Scholar


A. M. Bauer and M. Menegon . 2006. A new species of Prehensile-tailed Gecko, Urocotyledon (Squamata: Gekkonidae), from the Udzungwa Mountains, Tanzania. African Journal of Herpetology 55:13–22. Google Scholar


P. Beresford 2003. Molecular systematics of Alethe, Sheppardia and some other African robins (Muscicapoidea). Ostrich 74:58–73. Google Scholar


L. H. Brown, E. K. Urban, and K. Newman . 1982. The Birds of Africa Vol. I.Academic Press. London. Google Scholar


N. D. Burgess, T. M. Butynski, N. J. Cordeiro, N. Doggart, J. Fjeldså, K. M. Howell, F. Kilahama, S. P. Loader, J. C. Lovett, B. Mbilinyi, M. Menegon, D. C. Moyer, E. Nashanda, A. Perkin, F. Rovero, W. T. Stanley, and S. N. Stuart . 2007. The biological importance of the Eastern Arc Mountains of Tanzania and Kenya. Biological Conservation 134:209–231. Google Scholar


T. M. Butynski and C. L. Ehardt . 2003. Notes on ten restricted-range birds in the Udzungwa Mountains, Tanzania. Scopus 23:12–27. Google Scholar


W. S. Clark and C. Edelstam . 2001. First record of Cassin's Hawk Eagle Spizaetus africanus for Kenya. Bulletin of the African Bird Club 8:138–139. Google Scholar


T. R. B. Davenport, W. T. Stanley, E. J. Sargis, D. W. De Luca, N. E. Mpunga, S. J. Machaga, and L. E. Olson . 2006. A new genus of African monkey, Rungwecebus: morphology, ecology, and molecular phylogenetics. Science 312:1378–1381. Google Scholar


R. De Jong and T. C. E. Congdon . 1993. The montane butterflies of the eastern Afrotropics. In J. C. Lovett and S. K. Wasser , editors. (eds). Biogeography and Ecology of the Rain Forests of Eastern Africa Cambridge University Press. Cambridge. Pp. 133–172. Google Scholar


L. Dinesen, T. Lehmberg, J. O. Svendsen, and L. A. Hansen . 1993. Range extension and other notes on some restricted-range forest birds from West Kilombero in the Udzungwa Mountains, Tanzania. Scopus 17:48–59. Google Scholar


L. Dinesen, T. Lehmberg, J. O. Svendsen, L. A. Hansen, and J. Fjeldså . 1994. A new genus and species of perdicine bird (Phasianidae, Perdicini) from Tanzania: a relict form with Indo-Malayan affinities. Ibis 136:2–11. Google Scholar


L. Dinesen, T. Lehmberg, M. Rahner, and J. Fjeldså . 2001. Conservation priorities for the forests of the Udzungwa Mountains, Tanzania, based on primates, duikers and birds. Biological Conservation 99:223–226. Google Scholar


J. Ferguson-Lees and D. A. Christie . 2001. Raptors of the world Christopher Helm. London. Google Scholar


L. D. C. Fishpool and M. I. Evans , editors. eds. 2001. Important Bird Areas in Africa and Associated Islands: Priority Sites for Conservation Pisces Publications and Birdlife International. Newbury and Cambridge. Google Scholar


H. Friedmann and J. G. Williams . 1970. The Birds of the Kalinzu Forest, Southwestern Ankole, Uganda Los Angeles County Museum Contributions in Science 195Google Scholar


E. Haring, K. Kvaløy, J-O. Gjershaug, N. Røv, and A. Gamauf . 2007. Convergent evolution and paraphyly of the hawk-eagles of the genus Spizaetus (Aves, Accipitridae) - phylogenetic analyses based on mitochondrial markers. Journal of Zoological Systematics and Evolutionary Research 45:353–365. Google Scholar


A. J. Helbig, A. Kocum, I. Seibold, and M. J. Braun . 2005. A multi-gene phylogeny of aquiline eagles (Aves: Accipitriformes) reveals extensive paraphyly at the genus level. Molecular Phylogenetics and Evolution 35:147–164. Google Scholar


K. M. Howell 1993. Herpetofauna of the eastern African forests. In J. C. Lovett and S. K. Wasser , editors. (eds). Biogeography and Ecology of the Rain Forests of Eastern Africa Cambridge University Press. Cambridge. Pp. 173–201. Google Scholar


N. Hunter, C. Carter, and E. Mlungu . 1996. Recent observations in Udzungwa and Uluguru Mountains, Central Tanzania. African Bird Club 3:296–98. Google Scholar


T. Jones 2006. Kipunji in Ndundulu Forest, Tanzania: Distribution, Abundance and Conservation Status. Unpublished report for the Critical Ecosystem Partnership Fund, Fauna and Flora International and the Wildlife Conservation Society. 28. pp. [accessed 6 August 2007]. Google Scholar


T. Jones, C. L. Ehardt, T. M. Butynski, T. R. B. Davenport, N. E. Mpunga, S. J. Mchaga, and D. W. DeLuca . 2005. The highland mangabey Lophocebus kipunji: A new species of African monkey. Science 308:1161–4. Google Scholar


H. R. L. Lerner and D. P. Mindell . 2005. Phylogeny of eagles, Old World vultures, and other Accipitridae based on nuclear and mitochondrial DNA. Molecular Phylogenetics and Evolution 37:327–346. Google Scholar


J. C. Lovett 1993a. Climatic history and forest distribution in eastern Africa. In J. C. Lovett and S. K. Wasser , editors. (eds). Biogeography and Ecology of theRain Forests of Eastern Africa Cambridge University Press. Cambridge. Pp. 23–33. Google Scholar


J. C. Lovett 1993b. Temperate and tropical floras in the mountains of eastern Tanzania. Opera Botanica 121:217–227. Google Scholar


A. R. Marshall, J. E. Topp-Jørgensen, and H. Brink . 2001. Bird observations from West Kilombero Scarp Forest Reserve. In K. Z. Doody, K. M. Howell, and E. Fanning , editors. (eds). West Kilombero Scarp Forest Reserve – Zoological Report Report for the Udzungwa Mountains Forest Management and Biodiversity Conservation Project. MEMA. Iringa, Tanzania. Pp. 86–92. [accessed 6 August 2007]. Google Scholar


F. Rovero and G. Rathbun . 2006. A potentially new giant sengi (elephant-shrew) from the Udzungwa Mountains, Tanzania. Journal of East African Natural History 95:111–115. Google Scholar


F. Rovero, G. B. Rathbun, A. Perkin, T. Jones, D. O. Ribble, C. Leonard, R. C. Mwakisoma, and N. Doggart . (in press). A new species of giant sengi or elephant-shrew (genus Rhynchocyon) highlights the exceptional biodiversity of the Udzungwa Mountains of Tanzania. Journal of Zoology. Google Scholar


M. S. Roy 1997. Recent diversification in African greenbuls (Pycnonotidae: Andropadus) supports a montane speciation model. Proceedings of the Royal Society of London B 264:1337–1344. Google Scholar


M. S. Roy, J. C. da Silva, P. Arctander, J. Garcia-Moreno, and J. Fjeldså . 1997. The role of montane regions in the speciation of South American and African birds. In D. P. Mindell , editor. (ed.). Avian Molecular Evolution and Systematics Academic Press. London. Pp. 325–343. Google Scholar


W. T. Stanley, M. A. Rogers, and R. Hutterer . 2005. A new species of Congosorex from the Eastern Arc Mountains, Tanzania, with significant biogeographical implications. Journal of Zoology 265:269–280. Google Scholar


F. White 1981. The history of the Afromontane archipelago and the scientific need for its conservation. African Journal of Ecology 19:33–54. Google Scholar
Trevor Jones "Cassin's Hawk-Eagle Spizaetus africanus in Ndundulu Forest: a First Record for Tanzania, with Biogeographical Implications," Journal of East African Natural History 96(2), 187-192, (1 July 2007).[187:CHSAIN]2.0.CO;2
Published: 1 July 2007
Udzungwa Mountains
Back to Top