Cloacal microorganisms and mating systems of four Australian bird species

Polygamous mating systems are expected to put sexual partners at greater risk of contracting a sexually transmissible microorganism compared with monogamy. Potentially pathogenic cloacal microorganisms such as Candida albicans, Chlamydia, coliforms and non-lactose-fermenting bacteria were studied during the non-breeding and the breeding seasons in four avian host species: two polygamous (Malurus cyaneus and Sericornis frontalis) and two monogamous (Manorina melanophrys and Neochmia temporalis). The results indicate that the highly polygamous M. cyaneus harbours more coliform and non-lactose-fermenting bacteria (which can cause disease) in its cloaca than do the polyandrous S. frontalis and the monogamous M. melanophrys. In addition, we detected higher-intensity levels of the above bacteria in avian cloacae during the non-breeding season than during the breeding season. Although not significant, trends also suggest that monogamous host species are relatively less colonised by cloacal microorganisms than are polygamous host species, whereas the latter also suffer a higher degree of multiple infection than the former.