Black Stork Ciconia nigra occur widely from Western Europe to northern China and Japan, with non-breeding birds migrating annually to East Africa and the Sahel, northern India and eastern China. What makes the southern African population unusual is the fact that they are resident breeders, and are believed to undergo only regional migrations between seasons. Although the Black Stork of southern Africa have a widespread distribution, ranging from Zambia to South Africa, the population is fairly sparse, as these birds prefer remote areas and have particular feeding habits.
The Black Stork’s diet consists mainly of fish, caught in clear streams, estuaries and dams. Unlike Black Stork in Eurasia, which breeds in trees, the southern African population breeds on cliffs in remote mountainous regions. Breeding occurs during winter (May to July) when the birds can capitalise on the abundance of prey available when the water is receding. Although the southern African population is thought to have been isolated from the European population for quite some time, any possible genetic exchange between the two populations is yet to be confirmed.
In 1981 Dr Warwick Tarboton published a paper on the breeding status of the Black Stork in the (then) Transvaal. The paper presented findings on surveys conducted on 40 Black Stork nest sites that took place between 1976 and 1981. At that stage Tarboton estimated the Black Stork breeding population of the Transvaal to be between 50 and 70 pairs and, since most of the Black Stork’s breeding habitat was in remote areas least affected by a growing human population and by urban and rural development, concluded that the species was not threatened in the old Transvaal region. This paper represents the last known publication on the status of Black Stork in South Africa. Although much has been written about the migrating Black Stork population of Europe and Asia, any information on the status of the resident southern African population remains largely anecdotal. If one considers the severe environmental changes that have occurred since the publication of Tarboton’s paper in 1981, one must question how applicable these conclusions might be to the modern-day Black Stork populations of the North West, Gauteng, Limpopo and Mpumalanga provinces (i.e. the area previously known as the Transvaal).
Warwick Tarboton’s historical Black Stork nest records identified 62 regularly monitored nest sites between the late 1960’s and early 1990’s. BirdLife South Africa initially set out to resurvey these sites in July 2016. The aim was to assess the status of the South African Black Stork population. The results of these surveys will subsequently inform the future course of the project.
Surveying shy species such as the Black Stork is challenging, and further complicated because Black Stork breeding tends to be highly irregular, with pairs breeding in some years but not in others. This means that multiple surveys during the May to September breeding period over a number of years (at least three) is required to gain a reasonable indication of their presence in a particular area and their relative breeding success.
Current survey efforts are focused on the Waterberg and the Pafuri region of the Kruger National Park. Two surveys of the Luvuvhu River Valley in August 2017 and 2018 have only managed to locate a single active nest with a third survey scheduled for August 2019.
Changes in reporting rates of Black Stork between SABAP1 & SABAP2
We have observed major declines in the reporting rates of Black Stork between the first Southern African Bird Atlas Project (1987-1991) and the Second Southern African Bird Atlas Project (2007-ongoing). BirdLife South Africa is working to understand what is driving these declines and how to mitigate any of these potential threats effectively.