Months of the year

Figure 13.12 Seasonal changes in the distribution of four migratory raptors in West Africa. Grey shading - frequent sightings; blue shading - infrequent sightings. In this region, migratory raptors stay in the southern woodlands during the local dry season, while food is plentiful and hunting conditions are good. When it rains heavily and the grass grows rapidly to 1.3 m high, the migrants move north to the short grass areas, where the rains are later and lighter and produce less growth of vegetation. The birds thus manage to remain in a fairly favourable environment all year and, while in the north, they breed, taking advantage of a short seasonal surplus of food which is not fully utilised by the sparse resident population. Species differ in the extent of their migrations, and in the periods spent at different latitudes, depending on their particular needs, but the general northward passage occurs at the start of the rains in 'spring' and the southward passage at the end of the rains in 'autumn' (From Thiollay 1978).

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