Quantifying parasites is essential for understanding the ecological and evolutionary implications of parasites on their hosts. It is also crucial for many conservation attempts carried out in endangered groups of birds, like the Psittaciformes. The aim of the present study was to test for the presence of blood and intestinal parasites of Burrowing ... Parrots (Cyanoliseus patagonus) (Psittaciformes) breeding in a large colony at the Atlantic coast of Patagonia, Argentina. Although Burrowing Parrots in this colony have several blood-sucking ectoparasites, no blood parasite was detected in blood smears or with the use of a PCR detection method. Likewise, faecal samples of Burrowing Parrots contained no eggs or oocysts of intestinal parasites. We also review the literature on blood and intestinal parasites in wild Psittaciformes, showing that blood parasites were absent in all cases, and 20 out of 28 studies were negative for intestinal parasites. The observed apparent absence of blood parasites in Burrowing Parrots and other Neotropical Psittaciformes is in line with the theory that avian hemosporidians could have been evolved in the tropics of the Old World, where they are widely distributed and prevalent, and they probably penetrated to Central and South America through the Nearctic region of the Holarctic recently. The observed apparent absence of blood parasites could also be explained by innate immunity in Psittaciformes, as has recently been suggested for other long-lived birds.
