RT30: Quelea: (1) Integrated pest management versus lethal control: How should management strategies be improved? (2) Are migration patterns changing towards greater sedentariness?

Elliott, C. & Craig, A. 1999. Quelea: (1) Integrated pest management versus lethal control: How should management strategies be improved? (2) Are migration patterns changing towards greater sedentariness? In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban: 3216-3218. Johannesburg: BirdLife South Africa.

Redbilled Queleas Quelea quelea continue to threaten small grain cereal production in Africa south of the Sahara. Their depredations are currently effectively countered mainly by lethal control with organophosphate pesticides, but also in some countries with fire bombs. The costs of lethal control are usually borne by the Government, with little or no contribution from farmers. Under conditions of economic stringency, Governments are increasingly finding it difficult to find the resources to pay for lethal control which involves expensive pesticides or bombs, the use of aircraft and extensive vehicle-based ground support and surveys. In addition, recent research has revealed that the environmental consequences of using organophosphates for quelea control is potentially more serious than it was thought to be.

The RTD considered the possibility of promoting an Integrated Pest Management (IPM) approach to quelea control. It was explained that an IPM approach involves farmers in examining all aspects of farming practices in relation to quelea damage, seeking to minimise external inputs, especially pesticides. It includes modifying crop husbandry, planting time, weed reduction, crop substitution, bird scaring, exclusion netting etc., and using lethal control only for birds directly threatening crops when these other methods have failed. A major benefit of IPM is reduced environmental side-effects resulting from decreased pesticide use.

It was further suggested that the ‘quelea problem’ is sometimes more a result of farmer perception than a genuine threat to crops. Because quelea flocks are so conspicuous, they are often blamed for reduced crop production when other factors such as unfavourable rain, poor seed selection, insufficient land preparation, lack of fertiliser, failure to control weeds, badly organised bird scaring, shattering from late harvesting, and other influences, may all be contributing factors of equal or greater importance than the birds. On the other hand, in some circumstances, the threat posed by quelea is genuine and extremely severe local damage can be caused through no fault of the farmer. In the case of subsistence farmers, the loss of the crop can cause considerable hardship, and for commercial farmers profits can be much reduced.

IPM, as practised with increasing success in Asia, has developed methods of Farmer Field Schools and Demonstration Farmers as means of getting the message across, developing solutions jointly, and changing perceptions where appropriate. Such methods should be equally applicable in Africa for the quelea. Making farmers responsible for, and involved in damage reduction strategies, may reduce pressure on Governments for action. Commercial farmers should contribute substantially to the costs of lethal control, so that they are forced to evaluate whether the crop losses they incur justify the expense of the control. Programmes should also be developed with subsistence farmers that would give them incentives to comply with agreed procedures for reducing the vulnerability of their crops to quelea.

There was general support for the proposals, but there are practical difficulties. Considerable differences exist between commercial farmers (CFs) and subsistence farmers (SFs). For example, working with SFs to reduce weed infestations is useful for reducing crop attractiveness and improving yield (Sudan and Tanzania as examples), but SFs need to understand that once all fields in an area are weed free, quelea damage might still occur if the birds have no choice. CF fields, especially in southern Africa, are weed free, yet quelea attacks still occur.

In South Africa, concern about environmental side-effects of spraying the organophosphate fenthion has led to an increasing use of the fire bomb which has virtually no side-effects if carefully used. Half of the 200 interventions in the most recent season used this method. The cost of the firebomb is four times higher than that of fenthion, though the method achieves a 90% success rate compared with 60% for aerial spraying.

There was also concern that if farmers were asked to contribute to costs, they would tend not to report quelea concentrations and carry out their own control, with potentially much greater environmental harm if more toxic poisons were used or spraying was carried out improperly. Other countries expressed interest in the fire bomb technique as environmentally friendlier, and the need for interchange of expertise was emphasised.

In Zimbabwe, the main problem is commercial irrigated winter wheat, which attracts quelea as the only grain available at that time of the year. Sharing costs with farmers would need careful scrutiny, as it might be difficult to divide up the costs when several farmers are involved.

In Tanzania, there is evidence that birds do not readily eat certain varieties of sorghum, though their tannin content is not high. Further studies are required to determine how quelea will react if such varieties are more widely used. The scope for the substitution of quelea-vulnerable grain with maize, ground-nuts or soya beans was considered by the RTD as deserving further study especially among SFs. Often CF crop choice is dictated by price, but if CFs have to contribute to the cost of lethal control, this could alter the equations.

The use of quelea as food is highly developed in some countries like Chad. The capture and exploitation of quelea as food by farmers was considered by the RTD as a way of involving farmers even if the impact on quelea crop damage was likely to be minimal.

The RTD discussed the ecotoxicological effects of the two available avicides, fenthion and cyanophos. Fenthion has a high toxicity to aquatic fauna and its breakdown products are more toxic than the original active ingredient. The alternative cyanophos is less toxic to mammals and also appears to have a quicker knock-down effect on quelea, so that they are less likely to spread out from the spray site and contaminate raptors or other predators elsewhere. More studies are needed to clarify these potential advantages.

The management of quelea is complicated by their extensive migrations within Africa. In some areas, the birds' seasonal absences may offer respite from damage to crops maturing at certain times of year. Recent studies in South Africa suggest that some quelea populations may remain sedentary, causing crop damage at any time of year. The control of these and other strategic populations may be effective in reducing crop damage but requires the investigation of new reliable techniques to identify different quelea subpopulations, and better information on group cohesion and site-faithfulness.

The RTD first examined the existing theory of quelea migrations in southern Africa in which movement occurs in a Northwesterly Southeasterly direction from Botswana to the eastern areas of KwaZulu-Natal Province in South Africa and of Mozambique. The rainfall pattern and the resultant availability of fresh grass seed influence the timing of the movements back and forth along this axis. A link with the populations of quelea in Angola and western Botswana still requires elucidation.

Evidence collected from bird atlas work in South Africa indicates that a resident quelea population exists, showing little evidence of migration or of population fluctuation. However if the data are examined by habitat and altitude, two areas show significant seasonal increases in numbers. The highveld grasslands of Gauteng and Free State Provinces have an increased quelea population in winter, while a summer increase occurs in the lowveld of Botswana and Namibia. Such peaks in abundance indicate seasonal movement into these areas and support the NW/SE pattern.

Data from the 15000 quelea ringed in southern Africa and the 450 birds recovered, show widespread directional movements, with a trend to N/S rather than NW/SE if all data are tabulated. The inclusion of recoveries sometimes spread over more than one season, makes interpretation of directional movements less meaningful. There is also a bias in the distribution of ringers with more activity on a N/S axis than on a NW/SE one.

The RTD concluded that the atlas work needed to be extended to measure shifts of quelea populations rather than only presence or absence in a degree square. Ringing studies should look at short-term movements and target specific areas in an effort to clarify the origins of populations causing damage. This might allow strategic control of certain populations and the reduction of subsequent damage.

The RTD agreed to establish an e-mail network of those interested in quelea biology and management, and to investigate the possibility of producing an updated bibliography. A data-base on quelea records in southern Africa is in preparation at the Natural Resources Institute of the U.K, and, when complete, would be available for anyone involved in quelea research.