thus migrate between the temporarily wet areas within each of these five to six geographical regions. Each of the subspecies, as distinguished by different male breeding plumage, is confined to one or more of these geographical regions. In Nigeria, the nominate subspecies generally travels southwards during the start of the rains in the north during June and July, when the grass seed germinates, and is no longer eaten by the queleas. When they reach the Benoue River valley, for instance, the rainy season has already passed and the grass has produced new seeds. After about six weeks, the birds migrate northwards to find a suitable breeding area, nurture a generation, and then repeat this sequence moving further north. Some populations may also move northwards when the rains have started, to eat the remaining ungerminated seeds. In Senegal migration is probably between the southeast and the northwest. In eastern Africa, the subspecies aethiopica is thought to consist of two sub-populations. One moves from Central Tanzania to southern Somalia, to return to breed in Tanzania in February and March, followed by successive migrations to breed ever further north, the season's last usually occurring in central Kenya during May. The second group moves from northern and central Sudan and central Ethiopia in May and June, to breed in southern Sudan, South Sudan, southern Ethiopia and northern Kenya, moving back north from August to October. In southern Africa, the total population of the subspecies Q. quelea lathamii in October converges on the Zimbabwean Highveld. In November, part of the population migrates to the northwest to northwestern Angola, while the remainder migrates to the southeast to southern Mozambique and eastern South-Africa, but no proof has been found that these migration cohorts are genetically or morphologically divergent. Ecology and behaviour The red-billed quelea is regarded as the most numerous undomesticated bird on earth, with the total post-breeding population sometimes peaking at an estimated 1.5 billion individuals. The species is specialised on feeding on seeds of annual grass species, which may be ripe, or still green, but have not germinated yet. Since the availability of these seeds varies with time and space, occurring in particular weeks after the local off-set of rains, queleas migrate as a strategy to ensure year-round food availability. The consumption of a lot of food with a high energy content is needed for the queleas to gain enough fat to allow migration to