Genera of avian haemosporidian parasites infecting great tits at three altitudes in western Switzerland. Proportion (relative to each other) of avian haemosporidian parasites, by genus, recorded at a low, intermediate and high altitudinal study site in wild, breeding great tits (Parus major). Blue portions represent Haemoproteus sp. parasites, orange portions represent Plasmodium sp. parasites and green portions represent Leucocytozoon sp. parasites.