SEASONALITY OF MARABOU STORKS LEPTOPTILOS CRUMENIFERUS IN EASTERN AFRICA

SUMMARY Nesting by Marabou Storks in eastern Africa is seasonal, and so are assemblages of non‐breeding birds at places with a regular supply of food. In Uganda, where temperatures and day‐length are almost constant, Marabous have nested at about the same time each year, despite considerable variations in rainfall from year to year. However, rainfall can have a modifying effect, delaying egg‐laying by up to a few weeks. The timing of egg‐laying varied regionally throughout eastern Africa, but in general nesting began during a dry season and continued into the next wet season. In drier areas the timing of nesting was more complex. Regional variations in the nesting season, and in the sizes of feeding assemblages, are consistent with north‐south movements of individual Marabous to or across the equator, enabling them to avoid the late wet season and early dry season. These are times when the supply of natural foods is likely to be least. Figure 6 summarizes the data and indicates probable movements. In the wetter areas the main northwards movement is in October‐November, returning four to six months later. In driet areas the timing is almost reversed.