Friday, June 7, 2013

African traveler - the Marabou Stork

Recently, when catching vultures to fit them with satellite transmitters, we have incidentally caught a number of Marabou Storks – these we tagged before release in order to learn more about their movements. The tags are yellow patagial tags (attached to both wings), and each bird has a unique number engraved in black on its tags. The tags are quite conspicuous as shown in the photograph, but of course they are useless unless people know what to look out for, and to whom sightings should be reported. Information should be sent to Pete Hancock,, including the following details: date, locality (preferably with GPS co-ordinates), and tag number and colour. A digital photo would be very useful as the numbers can often be clearly seen on the image. It would be great if other people would use their networks to spread the word further, as we need wide coverage since we believe that these birds travel as far as central Africa. Why do we think our tagged birds will be seen outside Botswana when most southern African field guides state that the Marabou is resident and nomadic with local movements? Marabou Storks have very few breeding sites in southern Africa, there being a single colony (of about 30 breeding pairs) in Swaziland, while Botswana has the largest breeding population in southern Africa, of a mere 100 pairs. The species does not breed in South Africa or Lesotho, and there are a few minor sites in Namibia and Zimbabwe. Against this background, how does one explain the fact that in Botswana, the Marabou Stork often occurs in congregations of 3,000 to 5,000 birds? Could the relatively few breeding birds be maintaining a population of tens of thousands of storks? Or is it more likely that birds are coming to Botswana from elsewhere? Simple arithmetic, based on a clutch of two to three eggs per pair per annum shows that it would take a long, long time to produce this number of birds; it seems more probable that there is a regular influx of storks from further afield. Information on the movements of Marabou Storks has important implications for their conservation. It is speculated that the central African population in Uganda and Kenya (where the species has its stronghold) may well be providing most of the storks in southern Africa.

Tuesday, May 28, 2013

As the vulture flies ...

BirdLife Botswana, in conjunction with the CKGR Research Group and the Denver Zoological Foundation, recently deployed satellite tracking devices on a pair of adult White-headed Vultures in Khutse Game Reserve. These are the first birds of this species to be fitted with satellite transmitters to determine their movements. The White-headed Vulture is classified as Vulnerable on the IUCN Red Data List, but has been little studied and remains an enigmatic species. The White-headed Vulture research is part of a wider ranging Botswana vulture project aimed at providing a sound scientific base for their conservation. The five major Botswana vulture species are all globally threatened, and are nationally regarded as Birds of Conservation Concern. The White-headed Vultures were captured using a compressed-air powered cannon net, activated remotely from a concealed hide; this technique has been used by the team to catch relatively large numbers of Lappet-faced and White-backed vultures as well. The vultures were measured and weighed, and also fitted with unique numbered wing tags to aid future identification, before being released. Although it is early days yet, it is interesting to note that the pair has temporarily split up, with the male moving a few hundred kilometers northwards into the Central Kalahari Game Reserve; the female has remained in the vicinity of the capture site at Molose Pan in Khutse. Dr Richard Reading prepares to release the male (Photo: Pete Hancock). We would like to thank the Department of Wildlife and National Parks for their unstinting support of the project, and Kanabo Conservation Link for providing additional funding to facilitate the capture of the birds.

Monday, April 15, 2013

Birds and People # 37

Saturday, March 9, 2013

Pharaoh's Chicken visits Botswana

Photo: Brent Harris.

In southern Africa, the Egyptian Vulture is known affectionately as Pharaoh’s chicken, and is viewed with a great deal of interest since it is exceedingly rare. It is extinct as a breeding bird in our area, with the last definite breeding attempt in the region being in 1923. It is a vagrant to Botswana, and there have only been a handful of authenticated sightings in recent times, making it a Category A Rarity (less than 10 accepted records). It is not just in southern Africa that it is rare – it is regarded as a globally Endangered species and there is concern worldwide about its future survival and well-being. This species was last seen in Botswana during 1998, so the sighting of an immature bird at Wilderness Safaris’ Kalahari Plains Camp in the Central Kalahari Game Reserve caused a great deal of excitement in birding circles. The bird was seen and photographed by Brent Harris on 20th February, and the photos are quite conclusive. The bird is a subadult in its second or third year, with quite a bit of cream-coloured plumage which immediately differentiates it from an immature Hooded Vulture, the only other species with a slender bill (but which doesn’t normally occur in the Central Kalahari). Well done to Wilderness Safaris’ for recognizing the importance of this sighting and reporting it to the BirdLife Botswana Records Subcommittee.

Pete Hancock
BirdLife Botswana

Wednesday, February 6, 2013

Botswana's National Bird List

The recent addition of the Angola Cave-Chat to the Southern African bird list, and the ‘rediscovery’ of the Green Tinkerbird after a hiatus of 55 years, brings home clearly the dynamic nature of bird movements and distribution. Even in well-studied areas, bird checklists are always changing with the addition of new species and, regrettably, the removal of those which no longer occur. This recently-past Christmas and New Year has been an exciting time for birders in Botswana too. Just prior to this period, the BirdLife Botswana Records Subcommittee announced the acceptance of four additional records to the Botswana National Bird List: they are Lesser Yellowlegs, Rosy Starling, Shelley’s Sunbird and Long-tailed Pipit. This brings the current total for Botswana up to 591 species. However, this total is likely to be increased soon once the Christmas/New Year observations have been scrutinized by the Records Subcommittee. Andy Solomon couldn’t believe his eyes when he saw an African Pitta in his back garden in Maun, and had the good sense to call Mark Muller and Richard Randall to corroborate his sighting. The nearest regular locality for this elusive forest species is western Zimbabwe, but it is known as a migrant which sometimes overshoots its range and ends up in unexpected places. Photographic evidence of the bird’s presence was obtained, and this means that confirmation by the Records Subcommittee is something of a formality. On New Year’s day, an Isabelline Wheatear was seen at Lesoma, another exciting record! This presence of this species in Botswana has been somewhat controversial to date, with a claim by Hockey (1988) being subsequently rejected by the Botswana Bird Club Records Subcommittee (as it was then known - see Herremans, 1997). However, like the pitta, this is also a migrant, and so can pitch up in central and southern Africa irregularly. This is in fact a new record not just for Botswana, but for southern Africa, since previous records are in doubt. An Eastern Nicator from Kasane during December 2012 completed the trio. This is normally a tropical, coastal species which in this case, has probably moved up the hot, humid Zambezi Valley where suitable riverine woodland and thickets exist. It has previously been recorded regularly in extreme western Zimbabwe not far from the Botswana border i.e. it is extralimital, but its presence in Botswana is not entirely unexpected. It is important to emphasise that the jury is not yet out on these observations; nevertheless the point remains that birders who spend their Christmas birding are likely to be rewarded by very exciting sightings!

Saturday, January 26, 2013

Whose vulture is this?

Satellite tracking of birds is an expensive undertaking, but the results are invariably worth the cost. This has proved to be the case with a joint project being undertaken by BirdLife Botswana in partnership with CKGR Research and the Denver Zoological Foundation. The project aims to determine the movements of Lappet-faced Vultures in Botswana, specifically to ascertain whether the birds are able to meet their year-round requirements in Botswana’s large protected areas, or whether they scavenge in areas where they could be susceptible to poisoning by humans. The project is in its early stages, but to date we have captured five adult Lappet-faced Vultures using a cannon net, and attached satellite transmitters to all five – four in the Central Kalahari and one in the Makgadikgadi. The precise positions of the birds are recorded every two hours during the day, and initially it was clear that most of them were breeding as they remained in a fairly prescribed area around specific points which we presumed were their nests. Since the end of November, their home ranges have been expanding rapidly, and some spectacular movements have been undertaken. One particular bird made a long-distance foray into southern Namibia, and then returned a few days later, as shown on the map below.
It is important to note that the vulture flew southwest along the upper, slightly irregular route, and returned via the bottom route – which is incredibly straight, as though the bird was in a hurry to return and unerringly took the most linear course! The directness of this line-of-flight is uncanny – it would require a GPS or other navigational aid for a human to achieve this degree of precision! Apart from this feature, the 1,500 kilometre venture also raises some other interesting questions: Was this a deliberate sortie to a predetermined point for a specific purpose? What is at the place in Namibia where it turned around? Why did it return to its point of departure? It seems reasonable to believe that the foray was not accidental; wind direction is prevailingly from the east, and would have aided the bird on the outgoing leg of its journey, but hindered it on its return. It is clearly not being blown randomly throughout the region! When I asked Namibian colleagues what was at the turning point where the bird spent a short while before flying home, Chris Brown, Director of the Sustainable Solutions Trust and ornithologist of note, had the following information: “The map below shows the movement pattern, over more than five years, of a young Cape Vulture fitted with a satellite transmitter captured near Otjiwarongo by Maria Diekmann.
You will notice that the bird spent a lot of time in the Kalahari of south-eastern Namibia, in the same general area as your Lappet-faced Vulture. I went down there one weekend and spoke to the Manager of one of our Gondwana Parks/Lodges, Jaco Visser. Jaco grew up on a farm in the area and knows the farmers and their land uses. We had the specific farms on which the birds spent most time. Jaco immediately recognised these farms, not as game farms, but as commercial livestock farms where the farmers were well known to be poor farmers who regularly suffered high livestock mortalities. Most were sheep and goat farmers. I guess that, over time, these farms become areas well know to the vultures as profitable searching grounds and they keep an eye on what is happening there. The info system of vultures seems to operate at a SADC level!” This definitely adds another piece to the puzzle! It is apparently no coincidence that our bird should go down to the south-eastern part of Namibia to see what, if anything, was on offer there! The picture now emerging is as follows: Lappet-faced Vultures know all the good foraging areas in southern Africa, and it is quite simple for one of them to make a 1,500 kilometre round-trip to one of these locations to assess its current potential as a food source. A direct flight of 1,000 kilometres from the Central Kalahari could put a vulture in any one of seven southern African countries! Another Namibian colleague, John Mendelsohn, who was involved in monitoring the travels of several Cape Vultures said that ”Perhaps the most remarkable finding or all is that these birds avoided the Kgalagadi Transfrontier Park, rarely even crossing over its border for a sniff or look-see”. The information above immediately answers our fundamental research question about Lappet-faced Vultures: there is no protected area in southern Africa which is large enough to provide safety for this species from the potential dangers imposed by humans. In fact, the scenario is worse than ever anticipated – a single poisoning incident could annihilate a very large segment of the populations of all southern African vulture species, Lappet-faced included.

Sunday, January 13, 2013

Birds and People #36