Responses of birds to rainfall and seed abundance in the southern Karoo, South Africa

Resident and nomadic birds, both insectivores and granivores, were counted at 40 sites along a 200-km east-west oval transect in the southern Karoo. T otal species richness averaged 30.05 +/- 5.31 (S.D.) species per site, with less than half of the species being resident, and nomads and transients ma king up the remainder. There was a weak correlation between the number of i ndividuals of resident species and rainfall, but no significant correlation between number of individuals of nomadic species and rainfall. The numbers of resident insectivores were significantly correlated with the numbers of arthropods obtained in sweeps. There was no correlation overall between re lative seed abundance and numbers and biomass of granivorous nomadic birds, and no correlation between the numbers of resident granivores and the numb ers of seeds. The numbers of resident insectivores, resident granivores and nomadic granivores were correlated with the presence and abundance of ephe meral plants at some sites. There was a correlation between the average num ber of all birds at a site and the proportion of plants that were producing new growth, suggesting that the presence of new growth influences the loca l abundance of birds. (C) 2001 Academic Press.