The prevalence and density of infection with the haematozoan parasite Leucocytozoon marchouxi was studied in captive and free-living Pink Pigeons Columba mayeri on Mauritius between 1994 and 2002. Blood smears from adults, juveniles and squabs were screened. Overall prevalence of L. marchouxi was 30% and there were age class and year differences. Younger birds (≤ 1 year) were more often infected and had a higher density of infection than did older birds. High parasite levels were found in 6% of birds, all but one of which were less than 1 year old. Leucocytozoonosis has been recorded elsewhere in 20 out of 45 Pink Pigeons post-mortem and was the primary cause of death in 15 birds. However, we detected no significant difference in the survival of infected and uninfected birds examined in this study, suggesting that only subclinical infections were detected and any mortality was probably due to additional contributing factors such as concurrent disease and food shortages. A smaller sample of smears from other columbid species was collected to examine their role as reservoir hosts. The parasite was probably introduced to Mauritius with exotic columbids, which may be partially resistant, but the Pink Pigeon has acquired sufficient immunity now to be a maintenance host for the parasite.