On the Move Ies After Breeding

birding birding briefs briefs Two questions arise. 1970, an estimated 500 000 African Openbills were counted on the Kafue What the...? Flats. Since the 1980s, however, Kafue Where did all these birds Our readers kept track of the has been invaded by Mimosa pigra, Openbills as they made their way a thorny shrub from South America come from? And why did through the country. Here are two of that flourishes on seasonally inundated the letters we received. they move so far out of land. By 2005, more than 3 000 hec - their normal range? tares of floodplain had been lost, and itting on our veranda, we were aston- the weed continues to spread at an Sished to see African Openbills flying ever-increasing rate. Recent surveys overhead. They landed in the common January there were sightings from all at Kafue show that areas invaded by garden of our village, next to a dam along the eastern and southern sea- Mimosa support just one per cent of (below). Later they were joined by more boards between KwaZulu-Natal and the the number of Openbills compared to and we ended up with no fewer than Western Cape, with several reaching the pristine floodplain (Shamungu 2009, 11 birds in total. They are not known to Cape Peninsula, and extending up the Biodiversity 10: 56–60). Populations of occur in our region and we believe they West Coast at least as far as Verlorenvlei many other waterbirds have also been have never been seen here before. Could at Elands Bay. It is hard to estimate the severely impacted. this be climate change making them move total number of out-of-range birds, but The Openbill event follows on the out of their normal habitat? the irruption must have involved close heels of an irruption of Marabou Storks ANN CANNELL to 1 000 individuals. Leptoptilos crumeniferus into the Western NOTTINGHAM ROAD, KWAZULU-NATAL Two questions arise. Where did all and Eastern Cape in 2008/09. Both these birds come from? And why did irruptions occurred in summer. Out-of- n a recent visit to my house on the they move so far out of their nor- range Marabous were first recorded near OBreede River in the Overberg, I spent mal range? The breeding population Beaufort West in mid-December and the best part of 15 January slowly burbling of Openbills in South Africa is only a by early January there were flocks of along the river banks in my small rubber hundred or so pairs, begging the con- up to 70 near Port Elizabeth and more duck, admiring a profusion of waterbirds. clusion that they moved into South than 20 near Cape Town. As with the On a sandbank about two kilometres AFRICAN OPENBILLS Africa from further north. But quite Openbills, the numbers of Marabous upriver of Malgas, I spotted three birds BRIAN ALDRIDGE where is unknown. Vast numbers breed involved make it almost certain that the which in 40 years of being on the river in Zambia in winter and the timing of majority originated from outside South I had never before seen in this part of African Openbills’ the irruption suggests that they could Africa. Some remained around the Cape southern Africa. core range be birds dispersing from these colon- Peninsula until at least June 2009, but Such was my surprise that I hit the on the move ies after breeding. The only recovery have since disappeared. sandbank and went flying, thankfully The summer of 2009/10 will be remembered for the of a Zambian Openbill was that of a How long the Openbills persist in their without disturbing the birds. I identified unprecedented irruption of African Openbills throughout fledgling ringed in July on the Kafue new environment remains to be seen. them as African Openbills, and the follow- Flats and recovered six months later Whether there is any link between the ing day I returned to the location to make South Africa. in northern Namibia, indicating that factors driving the two stork irruptions is sure I hadn’t been imagining them – and Outliers (Upington, at least some Zambian birds do move unknown. What does seem highly likely, sure enough, there they were (opposite). Beaufort West) Irruptive range south after fledging. Irruptions often however, is that both species were driven This time I had my camera and was n a time of global change, birds climes (for example, Snowy Owl Nyctea involve young, naive birds, but adults south and west by deteriorating environ- able to record these unusual visitors to the and other organisms are predicted scandiaca irruptions in Eurasia and as well as juveniles were involved in mental conditions in areas where they south-western Cape. to change their ranges. Such move- North America). They are less common the recent movements. Interestingly, are naturally common. BRIAN ALDRIDGE Iments may be gradual, linked to changes in Africa, where they tend to be linked and Zululand, it is a rare vagrant to other there were also a few Openbills on PETER RYAN & PHIL HOCKEY CAPE TOWN, WESTERN CAPE in the distribution of suitable habitat, to rainfall. For example, during droughts parts of the country. The first record of the move in 2008/09, with one at such as the invasion of the Western Cape in south-western Africa, Dusky Sunbirds an out-of-range Openbill was a single Potchefstroom in mid-November and by Hadeda Ibises Bostrychia hagedash (see Cinnyris fuscus, Black-headed Canaries bird in the KwaZulu-Natal Midlands in another in the KwaZulu-Natal Midlands Africa – Birds & Birding 8(5): 35–41), or Serinus alario and Lark-like Buntings mid-November 2009. Three days later, in mid-December. It is possible that they may be sudden events, resulting in Emberiza impetuani occasionally irrupt 30 were found near Potchefstroom in small numbers of Openbills disperse only temporary range changes, typically into more mesic areas outside their the North West Province. By the end of south in early summer each year and driven by adverse conditions in their semi-arid habitats. Seabirds can also November a flock of 20 was seen in the that this event reached unprecedented usual distribution. have spectacular irruptions, such as the Midlands, and one bird was recorded proportions in 2009/10. Such rapid events are termed irrup- winter 1984 influx of Kerguelen Petrels near East London in the Eastern Cape. We can only speculate why the tions and are a fairly regular occurrence Lugensa brevirostris and Blue Petrels By mid-December birds had reached the 2009/10 irruption occurred. Conditions at high latitudes, where severe tem- Halobaena caerulea, which occurred Western Cape, with one near Beaufort in the Openbills’ normal range have peratures drive species towards warmer throughout the Southern Ocean, with West in the Karoo and another even not been exceptionally dry or wet, but birds reaching Brazil and Australia as further west on the Bot River, east of some of their traditional habitat has well as South Africa. Cape Town. Their numbers then start- been lost. Zambia’s Kafue Flats used The influx of African Openbills was The summer of 2009/10 will be re- ed to climb. By Christmas there were to be a key summer foraging area for monitored from locations as diverse as membered for the unprecedented irrup- sightings of flocks of 200 in southern Openbills, probably accommodating river banks in the Western Cape (above) tion of African Openbills Anastomus KwaZulu-Natal, 20 at Graaff-Reinet in birds from the vast Barotse floodplain and country gardens in KwaZulu-Natal lamelligerus throughout South Africa. A the Eastern Cape, and almost 50 near further west as water levels fall along (opposite). fairly common resident in the lowveld Riebeek West, north of Cape Town. In the upper Zambezi River. In November ANN CANNELL 8 BIRDING BRIEFS AFRICA – BIRDS & BIRDING APRIL/MAY 2010 BIRDING BRIEFS 9.

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