Couple of weeks back, precisely December 9th, 2017, I saw a news headline
"FG begins aerial spray against Quelea birds, other pests in Bauchi"
It was the first time I am reading such headline, I was able to isolate and interpret what “ pest” and aerial spray” is, but I had no idea what Quelea is, also I have not heard of aerial spray as mode of combating pest in Nigeria prior that time. So I promised to embark on a research into the new “ guy” Quelea compelling us to bring out agricultural fighter chopers/ jets. In my mind, I thought its another stronger novel pest, evolving from an older specie we already know, like the case of the fall army warm we had to deal with in 2017. I was wrong, Quelea is not new, as a matter of fact it has been described as far back as 1758 by Linnaeus and its preferred locality being India, this was however corrected to Senegal by Scater. Reichenbach in 1950 gave the bird the generic name Quelea.
Quelea is the most numerous bird species in the world with peak post-breeding population estimated to abount 1.5 billion. It is a small weaver bird native to sub-Saharan Africa and renowned for its attacks on small-grain crops within Africa. It feeds mainly on seeds of grasses, but when short of these seeds, or at personal will, when the opportunity arise, they will attack crops. Hence they become a dreaded pest. It is a major pest throughout much of sub-Saharan Africa and can cause significant economical losses. The bird is inherently nomadic, they migrate at will following rain fronts, and this nomadism accounts for its invasions into areas where they may be previously absent.
BREEDING
Quelea are small, short-tailed, sexually dimorphic weaver birds about 12 cm long and weighing 15 to 26 g. Eggs are laid in clutches of 1-5, usually 3, measure 18 x 13 mm and are bluish or greenish, occasionally with some dark spots. They build their nest in colonies, Some of these colonies are massive, stretching to up to 20 km in length and 1 km wide and involving millions of birds (such as at Malilangwe, Zimbabwe), with nests at densities of 30,000 nests per hectare. More than 6000 nests have been counted in one tree (Craig, 2010).
Nestling are born naked with wisps of down on shoulders and crown, with white bills. Eyes open and feathers appear on day 4. Within 2-3 months of hatching, juvenile birds complete a post-juvenile moult to resemble non-breeding adults, but with grey head, whitish cheeks and buff edges to flight feathers and wing coverts, followed 1-2 months later by a pre-nuptial contour moult, when they begin to assume the adult breeding plumages.
HABITAT AND BEHAVIOUR
They avoid forest, the Quelea is principally found in semi-arid areas of dry thornbush grassland such as the Sahel. It is also present in farmland, where it attacks crops. As it needs to drink every day, the red-billed quelea is always within about 30km of water. It is occasionally found in wet habitats and may congregate in huge flocks at edges of water-bodies, such as Lake Ngami, Botswana, when the lake floods. It requires bushes, reeds or trees in which to nest or roost. The red-billed quelea can be found up to 3000m above sea level but usually only occurs up to 1500m.
PREFFERED CROPS
Quelea have been recorded eating the following crops: barley (Hordeum vulgare), buckwheat (Phagopyrum esculentum), bulrush or pearl millet (Pennisetum glaucum), finger millet (Eleusine coracana), foxtail or italian millet (= manna Setaria italica), common or proso millet (Panicum miliaceum), oats (Avena), rice (Oryza sativa), sorghum (Sorghum bicolor and S. caffrorum), teff (Eragrostis tef), triticale (Triticum x Setale) and wheat (Triticum durum). Quelea do not attack maize on the plant as their bills are too small to cope with the large seeds, but they will eat crushed maize at feedlots. At the start of wet seasons, early maturing crops are in danger from adult birds on their early rains migrations and, later on in wet seasons, crops are particularly vulnerable to roaming flocks of juvenile birds that have recently left the nest. In dry seasons, irrigated crops are threatened by birds of all ages.
PHYSIOLOGY AND PHENOLOGY
Before migration, quelea build up their fat reserves by feeding on insects such as termites, with the amount of fat laid down linearly related to the distance to be travelled. Before breeding, protein-rich food such as termites and green grass seed is eaten, and reserve protein levels – the amount of labile stores in muscle sarcoplasm (Kendall et al., 1973) – reach a peak before declining, as they are used up by the efforts involved in reproduction (Jones and Ward, 1976
LONGEVITY
Wild birds tend to live for 2-3 years (Bird Trader, 2013), although they can live longer. A captive bird lived for 18 years and 9 months (Butler, 1913).
ACTIVITY PATTERN.
Quelea are thought to exchange information on locations of food sources when gathered at roosts or colonies (Ward and Zahavi, 1973). Huge flocks of breeding birds leave colonies and roosts in undulating streams at or just before dawn, apparently in directions of food or water sources, making a distinct noise due to numerous wing-beats. Small flocks return to roosts via a drinking site from 30 minutes before dusk, with numbers of arriving birds increasing as dusk approaches, sometimes in attenuated streams.
EXACTLY HOW DESTRUCTIVE CAN QUELEA FEEDING HABIT BE?
As described earlier, Quelea mainly eat grass and cereal seeds from the plant and from the ground, preferring grains 1 x 2 mm in size. When red-billed quelea need to build up protein, such as before migrations or breeding, quelea will feed on insects
A colony of more than 12,000 nests per hectare was estimated to have a monthly consumption of 1845 kg of seeds per hectare and 214 kg per hectare of insects (Craig, 2010).
The red-billed quelea has a substantial economic impact as a result of crop damage throughout sub-Saharan Africa. The crop damage occasionally necessitates imports of food aid, such as the 5,081 tonnes imported into Tanzania in 1942 (Brooke, 1967), or leads to famine, such as in Ugogo-land, Dodoma, Tanzania in 1881 (Haylock, 1959; Brooke, 1967).
A single quelea can consume and/or destroy up to about 10g of grain in a day (Elliott, 1989a). Thus, a flock of one million birds can ruin up to 10 tonnes of crop daily. When major invasions occur, crop damage can be as high as 50% of potential crop harvests and, locally, entire crops may be wiped out. The value of damage to small-grain crops was estimated as being equivalent to up to US$79.4 million
DAMAGE LEVEL IN NORTHERN NIGERIA.
According to report, over N6 billion worth of farm produce, equivalent to 50,600 metric tonnes of various crops representing 59 per cent crop has been lost to Quelea birds and other pest in farmlands in Bauchi State, with 17 local government affected. similar destructive activities were reported in other neighbouring states looks maraba and north western state of kebbi, where tons of rice are lost yearly to the bird's activities.
CONTROLLING QUELEA
1. Physical/Mechanical Control
If nesting birds with newly built nests or unhatched eggs are consistently disturbed they may desert colonies and move elsewhere. The harvesting of quelea for food, either directly from nests or indirectly by catching flying adults, may succeed in protecting crops if the colonies involved are not very big.
2. Chemical Control
Chemical control involves spraying with organophosphate avicides such as fenthion or cyanophos. The targets are concentrations of birds at roosts or breeding colonies. Spraying takes place at dusk, using either vehicle-mounted sprayers or aircraft. Dosages of 2-4 l/ha of fenthion are usual but occasionally they range from only 0.5 l/ha up to as high as 14 l/ha.
3. Host Resistance (incl. Vaccination)
Some varieties of sorghum such as Ark-3048 have low concentrations of tannins but high concentrations of the cyanogenic glycoside dhurrin, which is avoided by quelea.
4. Integrated Pest Management (IPM)
Combinations of cultural practices and harvesting of chicks or adults for food, or destroying nesting colonies, are possible IPM strategies. Traditional methods such as bird-scaring can also work.
CONCLUSION
Quelea are generally not a threat until their population builds up significantly. However it is important to not underestimate the bird. Farmers should work on physical destruction of the nest as soon as they are sited before they build up their population, they do not only become hard to control after they dominate an environment, they become impossible to eradicate. Even though it is obvious the birds predominantly target dry season farming in the north, it is important for farmers in southern part of the country to be sensitized as the Quelea bird specie are nomadic and have rich history of migration and introduction.
Aliyu Ahmed Olanrewaju
Researcher/Agribusiness consultant.
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