Blood parasites rupture mature red blood cells and so reduce haemoglobin concentration and hence the potential activity levels of infected males. We examined blood parasites and haemoglobin concentration in the superb fairy-wren (Malurus cyaneus) across three years and six locations in South Australia. We tested the prediction that males in nuptial plumage have more blood parasites and hence lower haemoglobin concentration than males in eclipsed plumage. Of 188 birds, 20 (10.6%) had blood parasites (Haemaproteus spp). We found that (1) there was an effect of season and sex on haemoglobin concentration; (2) there was no effect of haemoglobin concentration on prevalence of blood parasites or intensity; and (3) males in nuptial plumage had more blood parasites but higher haemoglobin concentration than eclipsed males.