Apparent Absence of Avian Malaria and Malaria-Like Parasites in Northern Blue-Footed Boobies Breeding On Isla Isabel

Abstract Haemosporidian parasites are common in birds, but often are not in seabirds. The absence of vectors/genetic resistance to infection have been proposed to explain this pattern. Examination of different host populations is required to confirm the absence of blood parasites in widespread host species, which could be differently exposed to blood parasites across their geographic range. Moreover, screening of blood parasites in many seabirds has been done only by visual inspection of blood smears, which can miss low-intensity infections. Screening of blood parasites of the genera Plasmodium, Haemoproteus and Leucocytozoon, combining inspection of blood smears and PCR-based detection methods, revealed that a highly philopatric colony of blue-footed boobies (Sula nebouxii) in the Tropical North Pacific is likely free of these parasites. Earlier detection of Haemoproteus parasites in frigatebirds cohabiting with boobies in our study site and blue-footed boobies breeding on the Galapagos Islands suggests that absence of blood parasites in this northern booby colony could not be attributable to the absence of vectors or genetic resistance to infection. High host specificity or fine-scale spatial heterogeneity in the abundance of insect vectors could explain our negative results, but these hypotheses remain to be tested. We emphasize the relevance of assessing the occurrence of blood parasites in different populations of widespread host species, such as blue-footed boobies.