1 2 3 4 5 6 7 8 9 10 The scourge of farmers throughout the continent, queleas are often referred to as ‘avian locusts’. Through sheer 11 12 weight of numbers they have the capacity to strip land bare overnight and despite the drastic measures that are 13 employed to control the population, they continue to thrive. Penn Lloyd examines the survival strategies that make 14 the quelea one of the most successful bird species on earth.  15 16 Ph o t o g r a p h s b y J & B Ph o t o g r a p h e r s 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62

  SmudgingSmudging the the sky sky likelike eddieseddies ofof smokesmoke 1 overover a a dying dying flame,flame, swarmsswarms ofof small 2 birdsbirds swirl swirl restlessly restlessly overover thethe trees,trees, 3 downdown to to the the water’s water’s edgeedge andand upup againagain 4 inin a a continual continual blurblur andand whirwhir ofof 5 6 flutteringfluttering wings. wings. TheThe birdsbirds flyingflying inin toto 7 drinkdrink at at the the waterhole waterhole areare Red-billedRed-billed 8 QueleasQueleas Quelea Quelea queleaquelea,, andand theirtheir 9 displaydisplay of of synchronous synchronous flyingflying givesgives the 10 impressionimpression ofof aa single,single, monstrousmonstrous 11 organismorganism rising, rising, fallingfalling andand swayingswaying 12 unpredictablyunpredictably overover thethe panpan withwith a 13 muffledmuffled roaring roaring fromfrom burstsbursts ofof frenziedfrenzied 14 15 flight.flight. It It is is impossibleimpossible toto tracktrack thethe 16 path of an individual – the energy of path of an individual – the energy of 17 thethe swarmswarm isis hypnotichypnotic ...... 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62

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  Watching and waiting, Tawny Eagles 1 gather while the quelea flock swirls 2 about them. It is difficult for predators 3 to single out individual prey in the 4 blur of movement. 5 6 7 8 ueleas are famous in the bird 9 Q 10 world for their spectacular aggregations. Massed flocks of literally millions of birds 11 on migration have been reported to dark- 12 en the sky as far as the eye can see. In 13 such flocks, as in their synchronized 14 flight at a waterhole, individual birds 15 merge into the blur of movement. This 16 loss of individuality fulfils an important 17 function, for aerial predators also have 18 difficulty singling out an individual from 19 the tightly-knit mass. 20 Queleas are members of the weaver 21 family and, like several of their cousins, 22 they are intensely social at all times. 23 They breed in vast colonies that can 24 number well over a million pairs. The 25 nests are crammed together in thorn 26 trees, or sometimes reedbeds, at a densi- 27 ty of up to 140 000 nests per hectare. 28 Colonies can cover an area that may 29 range from one to over a hundred hect- 30 ares, but is usually 10–20 hectares in 31 extent. Within each colony, breeding is 32 remarkably synchronous. The often 33 hundreds of thousands of pairs lay their 34 eggs within two or three days of each 35 other. When the females remove the 36 shells at hatching time, the falling egg- 37 shells sound like rain. After a further 38 week, the hungry screeching of the 39 young becomes deafening. 40 The chicks are fed insects, and par- 41 ents feeding several million hungry 42 and rapidly growing youngsters in a 43 colony can deplete over half the insects 44 within a 10-kilometre radius. Queleas 45 nest only after good rainfall has pro- 46 duced a flush of new plant growth, 47 resulting in an abundance of insects. 48 Nonetheless, this period of plenty is 49 short-lived and the birds breed in a 50 race against time. The male constructs 51 the loosely woven nest in about two 52 days, and the female generally lays 53 three eggs. The eggs hatch after just 54 9–10 days of incubation, and the chicks 55 leave the nest at the age of 11–13 days. 56 Their breeding is remarkably success- 57 ful, with 80–90 per cent of nests fledg- 58 ing young, undoubtedly because their 59 sheer numbers and synchronicity in 60 breeding swamp the available preda- 61 tors.  62 63

queleas 57  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Adult queleas feed on the seeds of The Tawny Eagle’s opportunity comes Queleas never attempt a second brood 32 annual grasses which ripen and are avail- when it swoops down to catch a weak or in the same colony, probably because 33 able in abundance several weeks after the injured bird trailing the flock. the conditions suitable for breeding do 34 rains. Once these seeds dry out and are not last long enough in one locality to 35 shed from the plants, they fall to the support two consecutive broods. 36 ground and become hidden under the However, a proportion of females begin 37 vegetation cover, making it difficult for to develop a new clutch of eggs while 38 queleas to access them until the grass they are still feeding almost fully-grown 39 cover thins out later in the dry season. nestlings. These birds, which are capable 40 Fortunately for the queleas, rainfall fronts of laying a second clutch within days of 41 advance slowly and predictably across dif- leaving the colony, undoubtedly conti- 42 ferent regions in Africa over a period of a nue their breeding migration by flying 43 few months, so that the rains begin and along the path of the rainfront to catch 44 end at successively later dates along the up with the zone of seeding grasses and 45 track of the front. Queleas take advantage 46 of this predictable variation in food sup- 47 plies by migrating back and forth along 48 the track of these rainfronts. They gener- 49 ally sit out the end of the dry season in 50 the region with the latest rains. By the Q.q. quelea 51 time the rains reach this region, seed will Q.q. aethiopica 52 be ripening after the early rains at the 53 other end of the rainfront track. Shortly 54 before the rains begin in the late-rainfall Map of Africa showing the suggested 55 migration patterns of different region, queleas gain weight by accumu- quelea populations. 56 lating fat to fuel their migration across From Bruggers, R.L. and Elliott, C.C.H. Q.q. intermedia 57 the full length of the front. Although 1989. Quelea quelea: Africa’s Bird Pest. Oxford University Press. Q.q. lathamii 58 they first have to cross an intermediate 59 zone where all seed has germinated and 60 Breeding Early rains the grass is still growing, they arrive to an migration migration 61 abundant food supply at the other end 62 and soon begin breeding.

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  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 breed again. By the time the dry season A Marabou Stork snaps up queleas individual farmers suffer serious losses 31 begins and their natural foods start to that have become waterlogged rather infrequently. Queleas seldom cause 32 become scarce, quelea populations have and have drowned at a waterhole under damage to the same local area in consecu- 33 increased several-fold after a sequence of the sheer weight of numbers of birds tive years. Recently, researchers have 34 successful breeding events through the coming in to drink. begun to question whether the ‘quelea 35 rainy season. It is now that their conflict problem’ has become exaggerated more 36 with man intensifies as they turn their as a result of farmer perception than as a 37 attentions to the abundance of food in genuine threat to crops. Because quelea 38 cereal croplands. flocks are so conspicuous, farmers blame 39 Despite having a distribution restricted the birds for reduced crop production, 40 to the savanna regions of Africa, the Red- when other factors such as limited rain- 41 billed Quelea has achieved notoriety as fall or poor farming practices may be of 42 ‘the most destructive bird pest in agricul- greater importance than the birds. 43 ture anywhere’ and ‘the most numerous When viewed at a national level, the 44 bird in the world’. Originally, the total magnitude of the damage is placed in bet- 45 population size was put at anywhere ter context. Estimates of such damage 46 between one and 10 billion, but the most vary wildly, partly because of the difficul- 47 recent estimate suggests that there are ties of assessment and partly because of 48 around 1 500 million (1.5 billion) queleas the vested interests involved. Figures of 49 across Africa at the end of a typical breed- up to US$59-million in damage per 50 ing season. The quelea’s status as a pest is annum have been quoted for some of the 51 rooted in the spectacular fashion in more seriously affected countries in East 52 which dense swarms can descend like and West Africa. However in 1989, Clive 53 locusts on agricultural lands and destroy Elliott, an ornithologist working on 54 grain crops within a matter of days. quelea projects for the Food and 55 The local damage can be devastating, Agricultural Organization (FAO) and 56 causing considerable hardship to subsis- United Nations Development Project 57 tence farmers in famine-prone regions (UNDP), estimated the continent-wide 58 and a significant economic loss to larger, damage caused by queleas to amount to 59 commercial farms. Consequently, farmers about US$22-million each year. If, for 60 universally regard the quelea as a serious argument’s sake, this damage is restricted 61 menace to food production, even though to the 11 countries which report  62 63

AUGUST/SEPTEMBER 1999 queleas 59  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 queleas as a major pest, then the loss The birds alight en masse in trees quelea breeding colonies are particularly 33 amounts to less than one per cent of their and reports exist of branches breaking vulnerable during quelea spraying opera- 34 total quelea-vulnerable crop production. under their weight. tions. The persistence of the poisons also 35 Nonetheless, the considerable local means that secondary poisoning is 36 damage that queleas do cause is difficult common. In some of the worst individual 37 to overlook and over the past 40 years incidents, 400 Black Kites were killed at a 38 millions of dollars have been spent try- colony in Mali, 200 White Storks died 39 ing to contain this threat through after eating poisoned queleas in Sudan, 40 research and lethal control. The main and big reductions in raptor populations, 41 control method now used is aerial spray- particularly those of Tawny Eagle, Augur 42 ing with organophosphate pesticides Buzzard, Black-shouldered Kite and Black 43 (fenthion and cyanophos). In the early, Kite, have been reported in Kenya after 44 exploratory days of lethal control, the ground and aerial spraying operations. 45 measures were extreme and resulted in Such catastrophic incidents are fortunate- 46 severe environmental contamination in ly infrequent, but are nonetheless an 47 many instances. In Senegal in 1956, ever-present danger. 48 more than five tonnes of explosives were Fire-bombs are finding increasing use 49 used to destroy 27 quelea roosts and 160 in some countries, particularly South 50 000 litres of diesel were used in flame- Africa, because of the reduced environ- 51 throwers to burn 3 200 hectares of mental side effects. Using 2 000 litres of 52 breeding colonies. In early ground- petrol per hectare, 20-litre metal drums 53 spraying operations in South Africa, dos- are spaced seven to 10 metres apart 54 ages of 2 250 litres per hectare of through dense quelea roosts or breeding 55 organophosphate were used, while as colonies, and connected to small quanti- 56 little as seven litres per hectare now suf- ties of explosives to detonate the petrol. 57 fice for aerial spraying. Poison baits and The bombs are set off after dark, once the 58 the poisoning of waterholes with cya- birds have settled in for the night, and 59 nide, once common practice, have large- shoot sheets of flames throughout the 60 ly ceased due to the indiscriminate kill- colony. The cost of the fire-bomb is four 61 ing of many non-target animals. times higher than that of fenthion, but it 62 Raptors attracted to the rich pickings at achieves a 90 per cent success rate com-

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  pared with 60 per cent for aerial spraying. 1 Lethal control operations are usually 2 the responsibility of government agen- 3 cies. The costs of control are thus borne 4 by the state, with little or no contribution 5 from farmers. Naturally, farmers are quick 6 to call in the control teams. In the face of 7 shrinking budgets, governments are find- 8 ing it increasingly difficult to pay for 9 expensive lethal control measures. There 10 is concern, however, that should farmers 11 be asked to contribute to the costs, or 12 should the operations be halted com- 13 pletely, farmers would carry out their 14 own, unmonitored control measures with 15 potentially much greater environmental 16 harm. Individual farmers are less account- 17 able than a government agency. For 18 example, in a bid to kill queleas, farmers 19 in Zimbabwe are known to apply a poi- 20 son designed for aphid control to the 21 edges of wheatfields. To further compli- 22 cate matters, recent research suggests that 23 claudio velÁsquez the environmental consequences of using 24 organophosphates for quelea control are Victims of the huge numbers of queleas 25 more serious than they were thought to that cram into a single tree, these 26 be. Among other findings, scientists have birds have been unable to avoid being Quelea control 27 discovered that the breakdown products impaled on acacia thorns. in South Africa 28 of fenthion are more toxic than the origi- 29 South Africa is one of the most efficient nal active ingredient. 30 countries in the lethal control of que- 31 In a new attempt to reconcile the con- leas. The Agricultural Research Council flicting demands of farmers and environ- is responsible for conducting research 32 mentalists, the FAO is now advocating an on queleas and control methods, while 33 Integrated Pest Management (IPM) the Department of Agriculture carries 34 approach to the quelea problem. IPM out the control operations. Since the 35 seeks to closely involve farmers in exam- 1950s, a relatively constant total of 36 ining alternative ways of reducing the 40–100 million queleas have been 37 risks of crop loss to queleas by modifying killed each year. 38 planting times, substituting crops, using Currently, the split between the use 39 bird-scaring techniques, and implement- of chemical spraying and explosions is 40 ing lethal control only for birds that are roughly even. Following a public outcry 41 directly threatening crops. This approach over the use of fenthion to spray reed- 42 is unlikely to find favour with hard-nosed bed roosts along the Gariep River sev- 43 commercial farmers who would favour eral years ago (fenthion is highly toxic 44 lethal control if they are not required to to aquatic life, let alone the rich diversi- 45 bear the costs, but it is thought to hold ty of waterbirds that use the 46 potential for reducing the losses of subsis- linear oasis of the river), it is the depart- 47 tence farmers over much of Africa. A ment’s policy not to spray queleas in 48 three-year experimental implementation wetlands. Only queleas that are a direct 49 and evaluation of the practicalities of IPM threat to crops are controlled, and the 50 is set to start in the Senegal River Valley rapid response times of the control 51 between Senegal and Mauritania soon.  teams ensure that minimal damage is 52 caused to crops. The threat of queleas 53 Author’s acknowledgements is therefore quantified as their potential 54 Much of the information used in this article to damage crops, which for the year 55 is derived from the book Quelea quelea: ending March 1998 was calculated at 56 Africa’s Bird Pest, edited by Richard Bruggers just over R7-million for the 75 million 57 and Clive Elliott. I am grateful too for addi- birds killed. The operational costs of 58 tional information supplied by Clive Elliott control amounted to a little over of the Food and Agricultural Organization 59 R3-million, excluding the costs of sala- of the United Nations, and to Henk 60 ries, transport, research and environ- Bouwman and Etienne van der Walt of the 61 Agricultural Research Council, South Africa. mental side effects. 62 63

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