Abstract:
This study evaluates the relative contribution of reproduction-based life history traits
and diet to the population trends in waterbirds from southern Africa. Life history traits (clutch
size, incubation period, fledging time, body mass and generation length), diet (prey weight, body
lengths and number of taxa represented in its diet (NTD)) and conservation status (declining/not
declining) of 163 waterbird species were reviewed. An index of diet generalism was created based
on NTD. Cluster analysis was applied on life history traits to define groups of waterbirds. Binomial
regressions were used to test if population trends were different across cluster groups and diet
variables. Four clusters of waterbirds were defined, with most waterfowl clustering together. Species
that feed on small and large prey had higher probabilities of declining (0.17 and 0.26, respectively)
compared to those feeding on medium-sized prey (0.08). Amphibians, coleopterans, crustacea,
molluscs and tunicates were used by species in all clusters, and the risk of waterbird populations
declining further are high given the current dwindling of the prey base. The large proportions of
declining species (61%) in waterbirds, which have constrained habitats, calls for continued efforts to
mitigate disturbances to wetlands.
