Patterns of distribution, species richness, endemism and guild composition of waterbirds in Africa
Publication Year:
Patterns of distribution, species richness, endemism and guild composition are identified for the water-birds of subsaharan Africa using uni- and multivariate statistical methods. When possible, our results are compared with similar information for South American water-birds. Water-birds partition Africa much more coarsely than do non-aquatic birds, the basic distributional dichotomy being between the west/central African forests and the equatorial and southern savannas. Also, unlike non-aquatic birds, African water-bird species richness is higher outside the tropics, exhibiting a longitudinal rather than latitudinal gradient. Water-bird endemism is also higher outside the tropics. In a stepwise multiple regression analysis only about 69% of the variance in water-bird species richness can be explained in terms of present-day environmental variation, especially measures of the abundance and length of rivers and the amount of lake shore-line. Part of the unexplained variance is attributed to historical factors, with areas of unexpectedly high species richness possibly acting as refugia during dry climatic phases. Analyses of water biotope availability and of 25 taxonomic, morphological, ecological and behavioural guilds suggest that habitat availability and quality are the primary factors which influence the above mentioned patterns. The subregion dominated by tropical rainforest is low in water-bird habitat diversity and quality, but temporally relatively uniform. The subregion dominated by savanna, on the other hand, is richer and more varied in water-bird habitat, but temporally much more variable. Relatively large, mobile taxa, such as the Anatidae, which utilize a variety of aquatic habitats, therefore predominate in the provinces comprising this subregion, and their high mobility is not conducive to the identification of avifaunal zones. Additional instances of the relative over- and under-representation of guilds in recognized water-bird zones are discussed.
Publication Title:
African Journal of Ecology
89 - 120
Item Type:
Journal Article