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Keywords:

  • community;
  • density dependence;
  • population abundance and growth rate;
  • rainfall;
  • raptor;
  • statistical modelling

Summary

  • 1
    We performed an extensive statistical modelling study on the population fluctuations and population growth rates of 15 raptor species in the Kalahari desert in South Africa.
  • 2
    The correlation pattern between rainfall and population abundance changed systematically with raptor body weight and diet type. The abundance of heavier raptors feeding on larger prey-items had lower correlations with rainfall than lighter raptors feeding on small prey-items. Whereas raptor species feeding on small prey-items were more affected by immediate rainfall, species feeding on large prey-items were more affected by rainfall in the previous year.
  • 3
    Population abundances were explained most parsimoniously by direct and delayed density dependence and rainfall during the current and previous breeding season. Interspecific competition was never a predictor variable. Population abundances of species best described by rainfall fed on larger prey-items than population abundances of species best described by density dependence.
  • 4
    Population growth rates were always best described by direct density dependence. The strength of density dependence was positively correlated with reproduction rate, due mainly to Falconiform species having higher reproduction rates than Accipitrid species.
  • 5
    Shifting from the species to the guild level, we found that abundance and biomass shares of feeding guilds did not vary significantly over time, supporting the hypothesis of guild constancy.