This species was historically abundant in Egypt, where millians were mummified as an offering to the god Thoth. By the end of the 19th century it had completely disappeared from Egypt. Urban expansion, habitat destruction, breeding disturbances and active hunting are believed to have contributed to the loss. Often called African Sacred Ibis, this is the thickest-billed of all members of the genus Threskiornis. The adults (back center) have unfeathered all black head and neck while the immatures (front) have their head sparsely feathered with whitish forming streaks and spots. This species has been lumped with the Black-headed Ibis (T. melanocephalus) of India, and the Australian Ibis (T. moluccus). Genetic studies show they have different chromosome karyotypes. For present species, three subspecies recognized by Clements et al. (2017). This is the nominate dark-eyed race found on the African mainland and Iraq. Two light-eyed races occur on Indian Ocean Islands. However Dickenson & Remsen (2014), Gill & Donsker (2018) and Matheu et al. (2018) all recognize them as a separate species, the Madagascar Sacred Ibis (Threskiornis bernieri) as recommended by Lowe & Richards (1991). Digiscoped with Panasonic DMC-LX5 | Nikon FieldScope III | 30XWA | hand-held (no adapter).
References:
Clements, J. F., T. S. Schulenberg, M. J. Iliff, D. Roberson, T. A. Fredericks, B. L. Sullivan, and C. L. Wood. 2017. The eBird/Clements checklist of birds of the world: v2017, with updates to August 2017. Downloaded from http://www.birds.cornell.edu/clementschecklist/download/
de Boer L. E. M., van Brink J. M. (1982) Cytotaxonomy of the Ciconiiformes (Aves), with karyotypes of eight species new to cytology. Cytogenet Genome Res 34:19-34.
Dickinson, E.C. and Remsen, J.V. ed. 2014. The Howard and Moore Complete Checklist of the Birds of the World. 4th ed. Princeton: Princeton Univ. Press. ISBN 978-0956861122
Gill, F & D Donsker (Eds). 2018. IOC World Bird List (v8.2). doi : 10.14344/IOC.ML.8.2. Available at http://www.worldbirdnames.org/.
Lowe, K. W.; Richards, G. C. (1991). Morphological Variation in the Sacred Ibis Threskiornis aethiopicus Superspecies Complex (PDF). Emu. 91 (1): 41–45. doi:10.1071/MU9910041. Retrieved 11 July 2018.
Matheu, E., del Hoyo, J., Christie, D.A., Kirwan, G.M. & Garcia, E.F.J. (2018). African Sacred Ibis (Threskiornis aethiopicus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/52753 on 10 July 2018).