FACTORS GOVERNING AVIAN BREEDING IN ACACIA SAVANNA, PIETERMARITZ-BURG, PART 1: EXTRINSIC FACTORS

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Abstract
Birds in Acacia savanna, Pietermaritzburg, bred mainly during the spring and early summer months (Sept.-Dec.) and the availability of food seems to be the major factor influencing the onset of breeding. Breeding activities ceased before the maximum food supply became available. In 1979 the fruit yield was high because of good rains the previous season so purely frugivorous birds started breeding 4 wk earlier in 1979 than in 1978. Partly frugivorous birds started a little later in 1979 but bred prolifically. The 1979 season was dry and high protein foods, such as insects, were less available. This resulted in less breeding by the purely insectivorous species. Heavy rain over short periods had very little effect on breeding activities but prolonged rains and low temperatures inhibited the starting of new clutches.