BLOOD PARASITES IN BRIGHT BIRDS: TESTING THE HAMILTON-ZUK HYPOTHESIS IN SUB-SAHARAN AFRICA WITH AN IMPROVED STATISTICAL METHOD

Abstract

Summary Underhill, L.G. & Kalejta-Summers, B. 1995. Blood parasites in bright birds: testing the Hamilton-Zuk hypothesis in sub-Saharan Africa with an improved statistical method. Ostrich 66:10-14. The data contained in a catalogue of avian haematozoa for sub-Saharan Africa were examined in the light of the Hamilton-Zuk hypothesis. The males of 464 passerine species were assigned six brightness scores. The generalized linear model with a binomial distribution and logistic link function is shown to be the appropriate statistical tool for analysing blood parasite data. With caveats, results from the model supported the prediction that bright males tend to be parasitized more frequently. However, the group of species with the highest brightness score, had infection rates similar to the dullest group. When phylogenetic associations were taken into account, support for the Hamilton-Zuk hypothesis was equivocal. Further research on the ecology and natural history of the interactions between blood parasites, their vectors and the birds they infest is needed to decide whether the differences between the lowest and highest infestation rates (23% for the dullest species and 37% for the penultimate brightness score) are biologically meaningful.