Lake Xau comes up to expectations

Thousands of Ruffs have now discovered Lake Xau.

Lake Xau has been a dry dustbowl for the past three decades. However the exceptional 2011 floods from the Okavango coursed down the Boteti River for over 250 kilometres beyond Maun to reach Lake Xau late last year. Birds have been rather slower than expected in finding this huge, shallow waterbody, but waterbird counts conducted by BirdLife Botswana member, Chris Brewster, over the Christmas period, show that it is well on its way to achieving recognition as an Important Bird Area (IBA).

One of the criteria for an area to achieve IBA status is that it should harbour significant numbers of globally threatened birds. In this regard, the key dryland bird species such as Bateleur and Martial Eagle, and Lappet-faced and White-backed Vultures (long resident in the area) are now being joined by globally threatened waterbirds such as Wattled Crane and Black-winged Pratincole. Congregatory waterbirds have not yet built up to numbers which exceed the critical threshold (0,5% of the global or regional population) but numbers of Ruffs and Great White Pelicans are already notable.

At present, it is the number of Black-winged Pratincoles at the lake (2,000) which is of special interest. In a recent article in Africa Birds and Birding magazine, Phil Hockey (Director of the Percy Fitzpatrick Institute of African Ornithology) suggested that this species might be in serious trouble. Very few pratincoles relative to 20 years ago are now being seen (cf the sighting of 10,000 by Penry and Tarboton at Lake Ngami during the 1980s). Phil Hockey suggested that the pratincoles may have shifted their non-breeding range northwards into northern Botswana but this is unlikely to be the case given the few sightings we have. Chris Brewster's count of 2,000 at Lake Xau is the best news we have had for this species in recent years, and highlights the importance of this 'new' wetland.

Apart from the pratincoles, there is much of interest to be seen at Lake Xau - it is certainly a spot worth watching!

Roadkill

Recently BirdLife Botswana member, Mike Soroczynski from Francistown contacted me to report significant numbers of hornbills being killed on the road between Dukwi and Kutamagore - he travels this stretch regularly on his way between Francistown and Mowana Copper Mine were he works. He writes "Its quite distressing to see the numbers killed. They seem to congregate at the roadside gravel verges only in the dry season - and coincidentally pror to the breeding season. I wonder what could be attracting them to such precarious areas? Seeds? Termites? Other insects? The gravel itself for egg production? Has anyone else reported such behaviour and fatalities?"
My wife, who is a long-distance cyclist, has reported the same high bird mortalities over a much wider area - she has cycled between Maun and Shakawe, Maun and Kasane, the Trans-Kalahari Highway and other routes and readily notices dead birds due to the (relatively) slow speed at which she cycles. In addition to hornbills, she has seen many Lilac-breasted Rollers, and various owls and nightjars, and a few years ago, large numbers of Barn Swallows following an early cold spell at the end of summer. She has also reported numerous snakes being killed, notably Puff Adders, and often Porcupines, Brown Hyaenas, Aardwolf and Bat-eared Foxes.

This Lappet-faced Vulture was killed during the breeding season, and probably had a chick on the nest which would also have died.

It is not known whether the effect of these mortalities on wildlife is sustainable, or whether it is depressing some populations. The latter is likely to be the case with globally threatened birds such as the Bateleur, and White-backed and Lappet-faced vultures, where numbers may already be low and/or declining due to a variety of threats. These birds sometimes scavenge along national roads and are susceptible to collisions with vehicles.
A beautiful chestnut-backed male Bateleur killed near Nata.

All sensible drivers in Botswana avoid driving at night due to the high probability of hitting a cow or donkey; we also need to take special care when driving during the day. Apart from the impact of roadkill on globally threatened birds and other animals, the impact of a 6kg vulture smashing through your windscreen will not do your vehicle much good either.It's in everybody'y interest to drive carefully . . .