While the African fish eagle Haliaeetus vocifer is one of the more iconic bird species associated with water bodies, the Western osprey Pandion haliaetus is a species not to be overlooked. Luckily for us, here in Plettenberg Bay on the Keurbooms River we have both of these magnificent species! The Western osprey is a slender, long- and narrow-winged raptor, with a wingspan of 1.5-1.7 m. It has white underparts and brown upperparts, with a dark mask through the eye and a white crown. Males and females can be told apart by the presence of a partial breast band in females, which is absent in males. They are usually associated with coastal lagoons and estuaries but can also be found further inland. They are also tolerant of humans and can be found in suburban, and even urban environments. The Western osprey is a Palearctic migrant, which regularly overwinters in South Africa. Birds of this species are generally solitary, and will migrate alone. While in South Africa they are generally silent but can produce a shrill whistle. They can often be seen on a dead tree overlooking the water, or occasionally hovering over the water while hunting. They hunt fish, and can plunge into the water feet first from a height of 50m! Historically, human persecution was a prevalent threat, but contamination of water bodies and by association fish is a concern. Due to a number of factors including the osprey’s almost worldwide distribution, and position as a top avian predator, they have been seen to be useful as sentinel species to monitor environmental contaminants in water bodies.
Written by: Minke Witteveen
For further reading:
- BirdLife International. 2016. Pandion haliaetus. The IUCN Red List of Threatened Species 2016. Accessed 2017-03-03. URL: http://www.iucnredlist.org/details/22694938/0.
- Grove, R.A., Henny, C.J., and Kaiser, J.L. 2009. Osprey: Worldwide sentinel species for assessing and monitoring environmental contamination in rivers, lakes, reservoirs, and estuaries. Journal of Toxicology and Environmental Health 12: 25-44.
- Sinclair, I., Hockey, P., Tarboton, P., Ryan. 2011. Birds of Southern Africa. Struik Nature, Cape Town. Pp. 93.