Effects of salinity on rates of infestation of waterbirds by haematozoa

A recent hypothesis suggested that migration patterns in waders and other b irds could be shaped by the distribution of parasites and diseases. This hy pothesis assumes a reduced exposure to parasites in species living in salin e habitats. To test this assumption, the number of species of haematozoa an d rates of infection reported for bird species living in fresh and salt-wat er habitats were compared. Species living in more saline habitats had fewer haematozoic parasite species than freshwater birds. Relative frequency of infection was also lower in saltwater species. Neither phylogeny nor the nu mber df individuals examined for blood parasites in each species explained these differences. Thus, there is indeed evidence that birds living in sali ne habitats have a reduced risk of being parasitized by haematozoa, probabl y due to a reduced abundance of the invertebrate vectors.