The Cape Bird Club
Cape Teal – A Global Rarity by Tony Williams
photograph by C.J.Uys
The Cape Teal should be appreciated for its global rarity!
The Cape Teal Anas capensis is an endemic to sub-Saharan Africa. There are two separate populations one centred on the saline lakes of eastern Africa and the other centred on ephemeral pans in southwestern Africa. Formerly the global population was guestimated by European based workers to be some 200,000 - 500,000. Peak count data from eastern African wetlands show that the eastern African population is only about 7000 and not the >100,000 previously claimed. Re-appraisal of the southern African population, based on CWAC counts data held at the ADU in Cape Town University, indicates a population in the range of 15,000 - 30,000 again not the 100,000 - 250,000 guestimated.
The natural breeding localities of Cape Teal are shallow and so ephemeral , brak to saline pans. As these often dry out they lack fish. As a result invertabrate prey especially the larvae of chironimid midges are more abundant than in permanent freshwater wetlands. Cape Teal are adapted to exploiting these resourses. Since the availablilty of ephemeral brakish wetlands depends on rainfall and this varies greatly from year to year the global population of Cape Teal probably ranges between some 40,000 individuals after good rains and some 20,000 after periods of several drought years with reduced breeding. If we take 30,000 as an average population, then the 1% of global population level at which a wetland is considered significant for conservation of a species is 300 Cape Teal.
Counts of the pairs of Cape Towns Strandfontein sewerage works show that in October to December this locality, regularly supports between 1000 and 2000 Cape Teals, effectively 3 - 6% of the global population. In 1964 Strandfontein supported 2386 Cape Teal the most ever recorded at a single locality.
Strandfontein is especially important for our understanding of Cape Teal because it has been counted at monthly intervals over many years and of all localities provides the best insight into seasonal changes in numbers. reduced numbers at Strandfontein in June to September are presumably related to the teal dispersing to breed. It mustnot be assummed that these are just birds breeding in the winter rainfall area. In summer rainfall areas, where most ephemeral pans occur nest records show that Cape Teal breed primarily in May to July. During these months water levels are more stable than during the summer when thunderstorm events can cause rapid shifts in water levels which can flood nests.
After breeding Cape Teal undergo, a full body moult during which they shed their flight feathers. They are then flightless for a period of 2 - 3 weeks and flight impaired for an additional week or so. The ephemeral pans where they mainly breed, dry out seasonally, and for safety during the moult Cape Teal move to large shallow water bodies. where they can swim out beyond the reach of mammalian predators and where there is ample food for them to regain condition after moulting. The pans at Strandfontein are evidently ideal for moulting teal, hence their global significance. The large numbers recorded there between October and January probably reflect the earlier moult of birds from the summer rainfall areas as well as the later moult of birds which bred at the wetlands in the winter rainfall areas.
In the early 1900's Stark and Sclater considered the Cape Teal scarce. Undoubtedly human provision of dams and other artificial wetlands and particularly large permanent ones like Strandfontein, has led to an increase in population. Nevertheless the population of the Cape Teal remains small relative to other global duck species, so next time you see a Cape Teal dont treat it as a trash bird - appreciate it for its global rarty as well as its attractiveness!
