Much fuss about nothing

In recent years, there has been much hue and cry about the spread of avian influenza by wild birds, fuelled in part by the related deaths of nearly 300 people. These deaths caused people to speculate that there could be a new pandemic in the human population, with the virus being spread rapidly by migratory birds which circumnavigate the globe annually. As always, rumours are fuelled by lack of factual information, and in Southern Africa in particular, there has been little information available on the Avian Influenza Virus and its prevalence in the region.

These fears have been shown to be unfounded by work done by Dr Graeme Cumming and colleagues working in Botswana, Mocambique, South Africa and Zimbabwe. They counted, captured and sampled birds at five sites in the four countries, one of which was Lake Ngami, and did not positively identify any highly pathogenic H5N1. They also found that the annual influx of Palaearctic migrants had no detectable influence on this situation i.e. the migrants did not bring the virus into Southern Africa as had been speculated.

Other avian influenza viruses were found at a low frequency in some waterbirds, especially dendrocygnid (whistling) ducks. The White-faced Duck (shown above) and the Fulvous Duck, both have an extensive range across Africa, and individuals from populations north of the equator may mix with Palaearctic duck species, such as the Garganey, that migrate annually to western Europe. However, these two species had no trace of the lethal H5N1 strain.

For more information, read the original paper (see reference below).

Reference: Cumming GS, Caron A, Abolnik C, Cattoli G, Bruinzeel LW, Burger CE, Cecchettin K, Chiweshe N, Mochotlhoane B, Mutumi GL and Ndlovu M. 2011. The Ecology of Influenza A Viruses in Wild Birds in Southern Africa. EcoHealth Journal.

Too much of a good thing?

With the Okavango River at its highest flood level for decades at present, there have been great expectations for good birding as water reaches areas that have been dry for a long time. Throughout the Delta, water levels are high, and this has had the somewhat unexpected effect of forcing wading birds into peripheral areas. The result is that the central parts of the Delta are noticeably devoid of birds.

July is the month for the African Waterbird Counts, and long-standing transects that have been counted in the Okavango so far are turning up very few birds. The heronries at Xakanaxa, Gadikwe and Gcobega have been surprisingly quiet, and the same applies to other areas. Water at Lake Ngami is deeper and more extensive than at any other time in the recent past, and waterbirds are conspicuous by their absence.

However, along the fringes of inundated floodplains such as the Khwai and Gomoti, birding is much better. Unusually, sizeable flocks of Wattled Cranes are being seen along the Khwai River, an area previously considered marginal for this flodplain specialist. These are likely to be birds forced out of their normal areas by high water, or they may simply be taking advantage of the improved conditions at Khwai. The Gomoti floodplain is teeming with Slaty Egrets, Glossy and African Sacred ibis and a variety of ducks and geese.
Glossy Ibis probing the shallow floodplain margins (Photo: P Hancock)

Please keep the BirdLife Office in Maun informed of any build-up of waterbird numbers anywhere in the Okavango Delta system.

Ringed Pratincoles at Lake Ngami

One of the ringed pratincoles (Photo: K Oake)

An observant Maun birder, Ken Oake, recently spotted two Collared Pratincoles with rings (bands) at Lake Ngami, and managed to get a clear photo of one of them. Unfortunately the number on the ring is not legible, making this a somewhat tantalising observation as we cannot be certain of the origin of the bird. It is most likely that it was among the 61 Collared Pratincoles ringed at the Lake during an AFRING training course in December, 2005, and if this is the case, it would mean that the pratincoles are returning to this important site. Only 283 Collared Pratincoles have ever been ringed, so it is great to get a resighting of one of them, even if the information is incomplete.

Birders at Lake Ngami should also keep a look out for other bird species with rings - for example, a large number of Kittlitz's Plovers were ringed there during the AFRING course, and none of them have been re-sighted or recovered to date.