lesser kestrels
f lashmob Kestrels in the Karoo an Zyl tographs Anthony v Text & pho
After leaving their roost in the early morning, the first stop for Lesser Kestrels 36 african birdlife is to warm up in the sun. Mark D. Anderson My list of ‘raptor wonders’ of South Africa includes one of the highest densities of Peregrine Falcons in the world found in the Western Cape, a population of one of the world’s rarest falcons, the Taita Falcon, in
Mpumalanga, aggregations of large migrant eagles in the Kruger National Bloemfontein Park, and raptor action at the Kgalagadi waterholes. But there is no doubt De Aar that at the top of the list are the huge flocks of Lesser Kestrels and Amur Cape Town Falcons that roost in the trees of many small towns across South Africa during summer.
above Hunting methods of There are three species of in Newcastle in KwaZulu-Natal, as appreciate this extraordinary raptor Lesser Kestrels (adult male small, hovering falcons that breed many as 28 000 Amur Falcons have phenomenon. shown) include catching in Europe and Asia and overwinter been counted in one evening. One invertebrates by searching in Africa. The bulk of the world’s of the largest roosts in the Karoo is rriving in De Aar during for them from a perch, by Amur Falcon Falco amurensis found in De Aar, and kestrel num- the day, there is little to hovering, or taking insects population migrates to southern bers there have been monitored for indicate that thousands of in flight. Africa, while the globally vulner- the past 15 years by volunteers of kestrelsA roost there. The surround- able Lesser Kestrel F. naumanni and the Migrating Kestrel Project, sup- ing farmland consists of a mixture of opposite At night, thou- Red-footed Falcon F. vespertinus ported by the Endangered Wild- dry grassland and Karoo bushes and sands of Lesser Kestrels overwinter in West and southern life Trust’s Birds of Prey Working is criss-crossed by a variety of fenc- congregate in their roost Africa and south-western Africa, Group. In the summer of 2012 an es, and by telephone- and power- trees, perching close to respectively. These falcon roosts estimated 12 000 Lesser Kestrels lines. If you look carefully, you each other in the canopy form some of the largest raptor ag- were counted at the De Aar roost may notice a kestrel perched every of the tree. gregations ever recorded; at one, and I spent some time there to so often on one of these poles, >
38 african birdlifeT Mark D. Anderson
above The burst of hun- although the birds are often diffi- to their roost in the town after birds could be accommodated in a There are several theories as to dreds of kestrels as they cult to see because they attempt to spending the day foraging out on single tree. why birds are social, but the two leave the roost in the morn- avoid the heat of the day by sitting the De Aar flats. As dusk approach- Interestingly, at Lesser Kestrel main reasons are to improve their ings is a spectacular sight. in whatever shade they can find. es, the clear blue Karoo sky gradu- roosts only the occasional twitter chances of finding food and to re- Low rainfall and high tempera- ally fills with falcons until the air is heard when there is a dispute for duce the risk of predation. The opposite, top Small groups tures have been shown to have an above the town is a swirling mass a particular perch. This is in direct chances of finding food are in- of kestrels forage over the adverse effect on kestrel survival. of small specks, each an individual contrast to Amur Falcon roosts creased by following other indi- Karoo during the day, and For instance, in years of low rainfall kestrel planning its roost spot. The where the birds’ constant chatter viduals to food sources, by roosting use fences, telephone poles in Africa, during which the birds’ activity is mesmerising as the birds causes the local townsfolk to com- close to available supplies, avoid- and power-lines as conveni- available food sources are reduced, switch between casual circling and plain about the noise. ing areas that have been depleted ent perches. half of the first-year kestrels, be- fast, twisting flights across the sky. To the inhabitants of De Aar, the of provisions, and even by using ing inexperienced foragers, die of As the light intensity fades, so the daily roost spectacle is simply part the roost as an ‘information cen- albert froneman opposite, bottom Small starvation while on migration in birds lose height until their action of another summer evening in their tre’ where areas of abundance can numbers of the migratory Africa. With temperatures increas- centres around the roost trees, with town and their daily activities don’t be communicated to others. The a flock, and ‘group resistance’ in certainty. One possible clue lies in Amur Falcons also occur at ing as a result of climate change, hundreds of kestrels each trying to seem to affect the kestrels. How- risk of predation can be reduced by which there is an abundance of in- how the kestrels leave the roost. Ka- the Lesser Kestrel roosts. The this could have serious long-term find a suitable perch. The way in ever, with so much open Karoo improved predator detection with dividuals to repel predators. roo mornings are characterised by a female Amurs (shown here) effects on the populations of these which the large blue gum and pine space available to the birds, it begs many more eyes to spot potential To date, no one has studied the feeling of anticipation – the town has are easily separated from small falcons. trees seem to ‘swallow up’ the kes- the question as to why they choose threats, having safety in numbers, roosting behaviour of Lesser Kestrels yet to wake up and the roosts are quiet the plain grey males. The spectacle begins in the late trels is impressive in itself as one to roost together, and especially in ‘the confusion effect’ which involves in South Africa so these questions and still. However, as it gets lighter, afternoon when the kestrels return would never guess that so many well-lit public places in towns. many individuals flying around in cannot be answered with scientific there is a tension in the air and >
40 african birdlife july/august 2013 lesser kestrels 41 above Roosts in towns with the abundance of cats and are well illuminated by owls prevalent in these areas, the street lights, giving the bright street lights could make kestrels good visibility nocturnal predators more easily (and thus presumably visible to the birds. In South Afri- increased predator detec- ca, the greatest number of mortal- tion) throughout the ities recorded at roosts have been night. caused by lightning or hail, while in the birds’ foraging areas cars are right Visitors to these the most significant killers. Karoo towns take note: Every year the scientific com- don’t park your car over- munity documents new raptor night under these seem- migration routes. The course ingly innocuous trees! followed by Red-footed Falcons moving between eastern Europe and south-western Africa, Lesser the occasional early-rising kestrel disperse so widely that, after seeing Kestrels between western Eu- can be seen zigzagging across the thousands at the roost in the early rope and West Africa, and the sky. Then, without warning and as morning, it is not easy to find ag- 14 000-kilometre trip by Amur if triggered by a silent alarm, a huge gregations of more than 20 kestrels Falcons between South Africa and flock erupts from the roost trees during the day. As kestrels find it China have now been accurately and the sky fills with thousands of best to spread out across the whole tracked. However, we still do not birds. At large roosts, there can be area, it suggests that helping each know if the Lesser Kestrels from several waves of these eruptions, other to find food is not the reason the Karoo take the same risks from the same and different trees. for their being social. as their Amur Falcon cousins, While the bulk of the kestrels may The answer to the roost ques- which fly for three days non-stop move off in a similar direction, tion probably revolves around across the sea on their way back staying together is only temporary predator avoidance. Although to their breeding grounds. There because, after a quick warm up in predation has not been well docu- are still many answers locked in the early morning sun, they scat- mented at roosts and urban en- these spectacular kestrel roosts in ter over a wide area. In fact, they vironments are not predator free the Karoo.
42 african birdlife