[1] Most biologists and ornithologists consider the red-billed quelea to be the most abundant wild bird species in the world. While exact numbers are difficult to determine, in part because of the population’s sheer size, it has been estimated that red-billed quelea number around 10 billion, with 1.5 billion breeding pairs. These birds live and breed in enormous nomadic colonies ranging from tens of thousands to millions of pairs. A large group of red-billed quelea can take up to five hours to fly past a given location.
[2] The red-billed quelea, also called the “weaver bird” because of its nest-making habits, lives exclusively on the African continent. It is a small finch-sized bird, with adults growing to approximately 12 cm long and weighing between 15 and 20 grams. The appearance of male and female birds differs depending on the season. The males breeding plumage is what is called “polymorphic,” with marked differences between individuals in feather coloring. The head and neck region of males may contain differing amounts of pink, purple, black, white, and yellow. Male breast and crown colors vary from yellowish to bright red, and they typically have a facial mask that ranges from white to black. These male colorings are seen in breeding season, outside of which adult males resemble their female counterparts. The bills of both males and females change during breeding season.
[3] The red-billed quelea is a communal breeder, with colonies achieving densities of 30,000 nests per hectare. The nests are built, or “woven,” by the male of the species in thorn trees, reeds, or other plants in the steppes and savanna regions of Africa. This takes place at the beginning of the seasonal rains, which varies depending on the region. The males take 2-3 days to build their nests before displaying their plumage to the females of the colony. Once eggs have been laid, usually in groups of one to five, an incubation period of 10-12 days ensues, after which the baby quelea hatch. Ten or eleven days later, the young birds leave the nest.
[4] The red-billed quelea colonies can fly long distances without tiring in search of food and foraging spaces. They work together as a flock, and when they find a suitable feeding place they can completely overwhelm the area with birds. They feed in a rolling formation along the ground, with birds at the back of a group leapfrogging to the front. Weaver birds prefer grass and small cereal seeds (though they will also eat insects if they have to), and when grass seed becomes unavailable, they may turn to human grain crops. For this reason, they are seen as pests by farmers, particularly in sub-Saharan Africa, and they have been known to cause significant economic damage to agricultural regions.
[5] Indeed, a colony of weaver birds, which may number in the millions, can wipe out entire crops. By some estimates, they cause $80 million per year of damage to small grain crops. In extreme cases, infestations of weaver birds have actually caused widespread famine and required the importing of food aid to make up for the shortfall resulting from crop damage.
[6] While the red-billed quelea might be incredibly destructive to human food supplies, the bird may actually improve biodiversity. With such numbers, the birds provide a reliable food source for many predators, including mammals, reptiles, and predatory birds. They even find their way into the human diet in the form of meat for kebabs and stews. Most other small species of birds, however, may be displaced when a colony of quelea descends on an area.
[7] Other environmental impacts include damage to trees where the red-billed quelea roost and the fouling of watering holes. Their overall impact is such that humans have actively attempted to control the species’ population. However, while, as many as 180 million birds have been killed, the overall population has remained healthy and they continue to damage crops and impact humans and other animals in many regions of Africa.
