1 1 2 2 3 The desert denizens of the north 3 4 4 5 5 6 A Thekla Lark, its crest 6 7 raised during a display in 7 8 an attempt to attract a 8 9 mate or expel a competitor. 9 10 10 11 11 12 12 13 ’SKENYA’S 13 14 14 15 15 16 16 17 17 18 18 19 19 20 20 21 BADLANDSBADLANDS 21 22 22 23 23 24 24 25 25 26 26 27 27 28 28 Sudan ust north of Nanyuki, 29 29 30 the Kenyan highlands 30 31 Lake 31 32 Turkana of ’s Great Rift 32 33 J 33 Chalbi Dida Galgalu Valley begin to fracture, 34 Desert Desert 34 35 • Marsabit and the great escarpment 35 36 Kaisut 36 Desert 37 alley crumples down to the 37

38 U ganda 38 39 Rift V Kenya Badlands, the sweltering 39 S omalia 40 Lake • Isiolo 40 Baringo • Nanyuki 41 lowland plains that stretch 41 42 from northern Kenya into 42 43 • Nairobi 43 44 Ethiopia and . 44 45 45 46 Keith Barnes describes 46 47 some of the special 47 48 48 49 adaptations of the 49 50 50 51 in this fascinating area, 51 52 52 53 and its links to other 53 ➥ 54 Old World deserts.  54 55 55 56 56 57 57 58 58 59 The barren lava plains north of Isiolo, stretching towards 59 60 Marsabit and Ethiopia, are the habitat of Masked and 60 61 William’s larks, the latter being one of Kenya’s seven 61 62 Text and photographs by KEITH BARNES endemic lark species. 62

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 1 1 2 Historically just 2 3 extreme races of the motionless until the danger had passed 3 4 same species, with the before they resumed standard activities. 4 5 separation of deserts When recently fledged finchlark chicks 5 6 by miombo woodland, are approached, they lie flat and immo- 6 7 the Purple Grenadier bile, heads outstretched on the sand, bills 7 8 (right) in the closed and eyes half closed, effecting 8 9 north-east has differ- excellent camouflage. When the parents 9 10 entiated sufficiently spot a potential predator, a warning call 10 11 from its sister taxon, can elicit this behaviour in their chicks. 11 12 the Violet-eared In Kenya, the Thekla Lark Galerida the- 12 13 Waxbill (far right) in kla inhabits the stony shores of Lake 13 14 the south, to be Turkana, a stretch of lava plains virtually 14 15 regarded as a devoid of vegetation and surely one of 15 16 different species. the most inhospitable habitats on earth. 16 17 The uses its prominent crest in 17 18 many aggressive encounters with neigh- 18 19 bours and in complex courting displays 19 20 but, when threatened, it can quickly 20 21 avoid detection by dropping its crest, 21 22 opening its wings and crouching next to 22 23 a stone, where it will blend impercepti- 23

24 TARBOTON WARWICK bly into the pebble mosaic. The crest is a 24 25 feature of many larks. It is not only a 25 26 fashion accessory, it also helps to regu- 26 A theoretical image of what Africa 27 unpredictable environment, one might late temperature; when raised during the 27 may have looked like during the 28 species have been recorded in East Africa; expect some larks to lay large clutches day it scatters solar radiation to divert 28 cold, dry Plio-Pleistocene cycles 29 in Kenya, 14 of the 21 species are found and have short lifespans, yet they don’t. unwanted heat, but at night it is used to 29 (far left) – a desert corridor 30 primarily in the arid zone. Typically writ- Most lay only two eggs, rarely three. trap a layer of air to insulate the head 30 stretching from the Somali Horn 31 ten off as LBJs, their variation in shape, Instead, larks seem to hedge their bets by against the desert chill. 31 to just outside Cape Town. 32 form and behaviour is dramatically laying as many clutches as possible dur- A lark’s activity is limited by ground 32 During warm, wetter intervals 33 under-appreciated, as is their ability to ing the favourable period. But why do temperature, and birds spend much of 33 (left), such as the conditions 34 eke out an existence where few other they do this? There are two possible the day crouching in the shade of bushes 34 prevailing in Africa today, the 35 birds dare to venture. explanations. The first suggests that losses or remaining inactive in an effort to 35 moist woodlands expand across 36 Kenya holds nomadic, resident and of eggs (which are laid on the ground) conserve water and avoid the expensive 36 central Africa, slicing the corridor 37 migrant lark forms; they are one of few and young to predators are enormous exercise of cooling down. Perhaps the 37 in two and fragmenting the 38 bird groups to display all three strategies (see Africa – Birds & Birding, ‘Hide & seek’, most taxing time is during breeding, 38 desert world into a series of desert 39 to cope with the erratic desert environ- vol.4, no.2). So rather than producing a when male larks are forced to abandon 39 islands that persist only in the 40 ment. Finchlarks are gregarious nomads single clutch laden with plump, edible their usual cryptic demeanour and soar 40 most geologically and climatically 41 and in East Africa flocks comprising up nestlings, they produce as many small into the sky, indulging in elaborate dis- 41 stable areas of the continent. 42 to 4 500 birds have been recorded. Their clutches as possible. In this scenario, it plays to impress potential mates. These 42 43 nomadism allows them to exploit envi- would be logical to find the birds relying typically involve an energy-sapping wing- 43 44 ons ago, when swathes of forest Dida Galgalu and Kaisut deserts of north- itably, the two became different enough ronments and food resources that exist heavily on camouflage, hoping that at clapping or undulating flight coupled 44 45 covered North Africa, Kenya ern Kenya, where desert birds have had to be regarded as separate species (Violet- for only the briefest moment in time, least a few individuals will escape the with complex singing. 45 46 Eencompassed the centre of a desert the most time to adapt themselves to the eared Waxbill/Purple Grenadier). This and their sociable networking in large attentions of adders and mongooses. The When birds fly, their massive pectoral 46 47 world that in its prime stretched from rigours of this demanding environment. process has happened with many differ- groups increases the probability of find- other explanation is that clutch size is flight muscles generate a substantial 47 48 Mongolia’s Gobi Desert to the scorching High body temperature, excellent insu- ent species and species groups, and at ing locally abundant, if rather patchy, smaller because food is scarce and unpre- amount of heat and, when the air tem- 48 49 sands of the Namib. Throughout the Plio- lation and their great mobility contribute many different times as the deserts con- resources – a situation typical of most dictable. In the deserts where chick star- peratures are extremely high, offloading 49 50 Pleistocene, a period some four million to to making birds some of the desert’s most tracted and expanded during wet and dry East African deserts. vation and egg mortality are high, the this heat becomes a problem. This can be 50 51 800 000 years ago, the earth’s climate successful inhabitants. A comparison of cycles. Groups where the resultant pat- Most birds have a more or less predeter- parents ‘gamble’, investing less effort in solved in a number of ways. By evolving 51 52 fluctuated enormously, and glacial cycles the Violet-eared Waxbill gra- terns of speciation are most obvious are mined breeding season, but many larks each breeding attempt, and more effort complex but multi-functional displays, 52 53 resulted in repeated periods of dry, cool natinus of southern Africa with the Purple the larks and sandgrouse. are ready to breed at any time of year. in producing more clutches, in the hope including activities where the skin is 53 54 weather interspersed with moist, warm Grenadier Uraeginthus ianthinogaster of Birds living in these ‘wastelands’ have Hormones maintain the organs of repro- that one will succeed. exposed (like leg-trailing or raised-wing 54 55 intervals. Some theorists suggest that East Africa best illustrates how Africa’s to cope with scarce and, even worse, duction in a permanent state of readiness. Much maligned for their dull colora­ advertisements), certain larks are able to 55 56 during the dry periods, desert corridors tur­bu­lent geological past drives desert unpredictable rainfall, temperatures that This permits the birds to begin develop- tion, larks’ cryptic plumage contributes attract mates and shed heat simultane- 56 57 connected the great African deserts (see speciation. These were once a single spe- fluctuate from extreme cold to extreme ing eggs within days of a breeding stimu- to the survival of their eggs, chicks and, ously. Furthermore, by displaying higher 57 58 maps above). During wetter times the for- cies, but its intolerance of the moist broa- heat in a couple of hours, and an unpre- lus. Finchlarks are known to lay eggs invariably, themselves. Although quite above the ground, where the air is cooler 58 59 ests expanded from Central Africa, leav- dleafed woodland that crept across most dictable food supply. The larks met this within weeks of a rainfall event, and to confiding at times, larks can reduce their and air movement is greater than it is 59 60 ing islands of desert in the most geologi- of central Africa essentially split the pop- challenge and have proliferated in Africa’s continue to raise subsequent broods for visibility at will; once, at the approach of nearer the ground, additional convective 60 61 cally and climatically stable areas of the ulation in two. Each popu­lation followed deserts, where they are arguably the most as long as favourable conditions persist. a harrier, I observed some finchlarks cooling can be achieved. 61 62 continent. These included the Chalbi, its own evolutionary pathway until, inev- successful group of birds. Some 38 lark Being nomadic and gregarious in an crouch under rocks and others remain Sandgrouse are another major group  62

48 kenya’s northern deserts africa – birds & birding october/november 2000 kenya’S NORTHERN DESERTS 49 

  1 1 2 2 3 the risk of being attacked by falcons and that give this species its odd appearance 3 4 other aerial predators. Larger flocks have and name are thought to play a vital role 4 5 a greater chance of detecting a swooping in regulating its temperature. All guinea- 5 6 predator than a smaller flock. By joining fowl are obligate drinkers and are limited 6 7 a larger flock each individual can reduce by the availability of water. The Vulturine 7 8 the amount of time spent watching for Guineafowl, however, has an exception- 8 9 predators. As most aerial predators prefer ally long caecum, the portion of the 9 10 to hunt by directing their attacks at sin- intestine involved in water re-absorption. 10 11 gle, isolated individuals, an individual in The modified caecum permits it to regu- 11 12 a large group stands a smaller chance of late and limit water loss to the extreme, 12 13 being attacked than if it were by itself. lessening the necessity to drink. 13 14 Furthermore, the sight of hundreds of Living in extreme environments – for 14 15 birds alighting simultaneously often cre- example intense heat, intense cold and 15 16 ates confusion in the mind of the preda- scarce water – tends to bring out the 16 17 tor, providing enough time for potential most remarkable adaptations in . 17 18 The White-headed Buffalo Weaver, The spectacular Vulturine Guineafowl. The facial skin acts as a prey to escape. Fischer’s Starlings flock, sometimes in huge Birds such as larks and sandgrouse seem 18 19 common in Kenya’s Badlands. radiator in the desert heat, cooling the bird down. This is the only Larks have solved the water quandary numbers, which enhances their ability to to have perfected these survival strate- 19 20 guineafowl that is able to go for many months without drinking. in a completely different way to sand- find locally abundant but spatially patchy gies in this uncompromising domain. It 20 21 grouse. They maintain high metabolic food resources in East Africa’s arid zones. is these adaptations that predispose 21 22 to have succeeded in exploiting Old remarkable behavioural adaptations to from the surrounding air. As a last line of rates so that a maximum amount of inter- them to taking advantage of new niches 22 23 World deserts, particularly in southern regulate body temperature, and have defence, gular flutter is employed to nally produced water is extracted from slightly different way. The size of the as the desert world expands and con- 23 24 Africa and Kenya. Of the world’s 16 spe- been likened to reptiles. They bask in the reduce body temperature and enables their food during digestion. When com- Vulturine, the world’s largest guineafowl, tracts over geological time, driving spe- 24 25 cies, 11 occur in Africa’s deserts and five sun in the early morning or on cold days them to keep their body temperature bined with low rates of water loss to evap- is apparently related to its preference for ciation and resulting in their domina- 25 26 are found in Kenya. Sandgrouse are and avoid overheating by flying during below 42 °C, even when air temperature orative cooling, this reduces the need for open habitats in the semi-deserts of the tion of the Old World deserts. Perhaps 26 27 thought to have evolved in Africa during the cool morning or evening hours. At exceeds 50 °C. Although the evaporative regular drinking. Horn of Africa. Here its head protrudes in retrospect, then, it is not so surprising 27 28 the Upper Cretaceous period, when most midday they crouch under bushes and at cooling gained from gular flutter is an Like the larks, the Vulturine Guinea­ over most of the scrub, enabling it to that the avifaunas of Kenya’s Kaisut and 28 29 of Eurasia was covered in subtropical for- night they huddle together to conserve effective way to lose excessive heat, sand- fowl Acryllium vulturinum hardly drinks at ‘peer’ at predators without being vulnera- Namibia’s Namib deserts share more 29 30 est. During the Middle Tertiary, when the energy. The soles of their feet, which grouse pay a high price by losing precious all and it has solved this problem in a ble to attack. The bare neck and head than just a superficial resemblance.  30 31 great Palaearctic deserts devel- water. 31 32 oped, sandgrouse moved into Despite being such successful 32 33 Eurasia. Although the taxo- desert residents, sandgrouse 33 34 nomic affinities of sandgrouse and their chicks have to drink 34 35 are uncertain, most authorities on a daily basis and they have 35 36 consider them to be most close- developed two major adapta- 36 37 ly related to waders. tions to achieve this. Their 37 38 Ironically, the basic anatomi- strong, pointed wings allow the 38 39 cal and physiological equip- birds sustained flight of 60–70 39 40 ment evolved by waterside kilometres per hour, which 40 41 waders has pre-adapted sand- helps in the search for tiny, far- 41 42 grouse to the desert world. In flung water puddles in a vast 42 43 common with waders they lay ocean of unrelenting sand, and 43 44 cryptically coloured eggs on their sponge-like belly feathers 44 45 the ground, have chicks that can absorb and retain water for 45 46 are able to walk within a day the long return flight to the 46 47 of hatching, possess pointed Black-faced Sandgrouse indulge their daily ritual of coming chicks. Sandgrouse also time 47 48 wings and strong muscles for in to desert puddles to drink and to absorb water in their their flights to water impecca- 48 49 flying great distances, and breast feathers for the long journey back to their chicks. bly, either in the early morning 49 50 spend a great deal of time or late afternoon. Although 50 51 walking on strong legs. Furthermore, often have to endure contact with scorch- they forage independently, they arrive at 51 52 they have a short bill, neck and legs – ing ground, are very thick and cov­er­ed waterholes in large flocks, and their char- 52 53 much like the seedsnipes, aberrant seed- with small, callous-like scutes. When acteristic overhead calls to others of the 53 54 eating waders from an ecologically simi- temperatures exceed 31 °C, sandgrouse species may serve to co-ordinate the syn- 54 55 lar environment in South America. initially employ wing drooping to cool chronous sandgrouse ‘happy hour’. 55 56 Like the larks, their cryptic plumage down, exposing the sparsely feathered Having arrived at the chaotic waterhole, 56 57 helps hide these birds as they spend long under-wing skin to the air. Once the air drinking and departing are rapid. 57 58 hours foraging in the open for seeds. temperature exceeds body temperature Their flights to and from waterholes are 58 59 Sandgrouse seldom squabble, which may they do something very odd indeed – the only times during the day that the 59 60 be to avoid detection by predators or they huddle together. By keeping the air sandgrouse abandon their otherwise 60 61 unnecessary energy expenditure in hot surrounding them at body temperature, unobtrusive demeanour. It seems clear 61 62 environments. They also exhibit some they reduce the amount of heat gained that they flock when drinking to reduce The dramatic Baringo escarpment at the edge of the Badlands, and one of Africa’s best birding sites. 62

50 kenya’s northern deserts africa – birds & birding october/november 2000 kenya’S NORTHERN DESERTS 51 

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