On our recent trip to both Gonerazhou and Lake Kariba, we were extremely lucky to see the near-threatened African Skimmer. These birds are partial intra-African migrants, arriving in southern Africa when the water level of rivers starts falling at the beginning of the dry season, returning northwards after breeding when rivers start rising again at the start of the rainy season. They inhabit wide open rivers, or marshes which provide dry open sandbars on which they need to breed and calm water in which to feed.
Their most distinctive feature is their bright red beak, with its upper mandible being significantly shorter than the lower. This much longer lower mandible they use to drag along the calm surface of the water when in flight, to catch small fish. The bill snaps shut when it touches a fish, which is then swallowed in flight or after landing. African skimmers feed mostly at dusk, dawn and during the night, (they have very good night vision) and rest during the warmer day when their fish prey is less likely to be at the surface of the water.
Pairs of African skimmers nest in loose colonies on large sandbanks, where they can lay up to three eggs over several days, into a small hollow in the sand. The eggs are incubated, primarily by the female, for around 21 days, after which the buffy-white chicks hatch.
The colonies of eggs are vulnerable to being trampled by hippos and elephants and to raising river water levels which could destroy an entire colony. Numbers of the African skimmer are believed to be declining; the result of numerous impacts on their wetland habitat. The construction of dams has flooded habitats upstream and altered the flow downstream, destroying suitable breeding habitat. The spraying of DDT to control malarial mosquitoes, tsetse flies and agricultural pests, along with other water pollutants, accumulates in fish and can be damaging to fish-eating birds such as the African skimmer. Humans and cattle can disturb colonies with fatal consequences for eggs and chicks, and the collection of eggs also occurs in some areas. The African skimmer may also be impacted through declines in their food supply caused by pollution, over-fishing and the effects of introduced predatory fish. It is believed that only 10,000-17,000 mature individuals remain in the region.
It is always exciting seeing these feathered creatures arriving back on our rivers, and it will be a sad day when they never return.