Zambezi River Sand-Bank Breeders

by Pete Roberts
(Victoria Falls - 19th July 2011)

Migrating birds such as the African Skimmer (Rynchops flavirostris ) are arriving to breed on the freshly sculptured sand-banks which emerge from the receding river. Despite the dangers of nesting on sand banks regularly trampled by hippo, predated by monitor lizards, and even disturbed by humans, skimmers and other birds such as lapwings and plovers return to successfully breed on the river each year.

The characteristic skimmer is an inter-Africa migrant, spending July to November on the Zambezi. A medium sized bird, long-winged and tern-like in flight, with brownish-black upperparts, white underneath and deeply forked tail, has a uniquely extended lower bill, which is noticeably longer than the upper mandible.

It has been estimated that nearly 1,500 skimmers breed along the river, representing 10% of the continent-wide population, conservatively estimated at just 15,000 birds. This highly significant percentage identifies the Zambezi as a key area of conservation importance for this enigmatic species.

The birds disperse widely after the breeding season, which occurs in the dry season when rivers are at their lowest and the sandbanks most exposed, migrating up and down large river systems and to and from inland lakes. They occasionally frequent coastal lagoons, salt-pans, open marshes and estuaries, although less commonly.

The skimmer feeds on fish, such as cichlids, and forages in a unique manner, namely by skimming the water in flight with its mouth open and extending its elongated lower mandible just below the water’s surface, leaving a wake as it moves. The bill snaps closed as it encounters small fish.

There are currently no specific conservation measures being undertaken to protect the species, although it is listed as ‘Near Threatened’ by the international conservation community and the population is thought to be declining. Part of the problem is that the Skimmer’s breeding habitat is stretched along a huge distance of the Zambezi river, and consequently through many different countries, needing conservation action to be co-ordinated at regional or continental level.

Human disturbance is thought to be largely responsible for the gradual but steady decline in African Skimmer populations throughout its southern African range. Its breeding areas have been much reduced by human management of river systems, in particular dam-building, which causes flooding in upstream areas and smaller flows downstream. Other forms of disturbance, such as egg collecting, trapping of the adult birds and indirect disturbance (such as increased boat traffic) have all impacted on the species' breeding success. The wave action of motorboats flooding nests, dislodging eggs and disturbing incubating adults is often been cited as a contributing factor to declining numbers.

If you are on a boat trip on the Zambezi at this time of year, please pay special attention for nesting birds. Whilst exposed sandy islands may be inviting for a quick stroll or sundowner, disturbing breeding birds can result in their failure to raise young. Watch out for skimmers and other ground nesting birds, and insist to your guide that you do not land on islands with breeding birds (a good tour guide will be well aware of this!). Always travel at a responsible speed.


Gone Birding

Birding trips on the river, in a small manoeuvrable boat and with an experienced guide, can be extremely rewarding at this time of year. There’s many species of herons, egrets, storks and plovers to be found, as well as a variety of other species. The islands offer a variety of habitats, and the receding river levels expose new feeding areas. Morning is best (purely because of the volume of traffic on the river in the evening with many larger boats operating ‘sunset cruses’ in various forms).

Specialist birders should contact us for advice on recommended local guides. Those less interested in ‘ticking-off’ species after species and more interested in the wider natural history and beauty of the experience will find a general guide more suitable. Morning trips are also great for photography, although you do have to be on the river as early as possible (and remember – it’s cold in the mornings!!).

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