Aims: To characterize the bacterial composition of mallard duck faeces and determine if novel bacterial species are present that could be utilized as potential indicators of avian faecal contamination. Methods and Results: Combined samples of fresh faeces from four ducks were serially diluted and plated onto six different media selected to allow the growth of a range of organisms at 42 degrees C under three atmospheric conditions: aerobic, microaerophilic and anaerobic. Forty-seven morphologically dissimilar isolates were purified and partial sequencing of the16S rRNA indicated at least 31 bacterial species. Twenty of these could be identified to the species level including pathogenic species of Bacillus, Campylobacter, Clostridium and Streptococcus. Other species identified included: Enterococcus, Escherichia, Megamonas, Cellulosimicrobium, Neisseria, Staphylococcus and Veillonella. Potentially novel species, which could represent bacteria specific to avian fauna included Bacillus, Corynebacterium, Macrococcus and Peptostreptococcus, while four isolates had < 97% similarity to known bacterial species in the available databases. Conclusion: A survey of the natural microflora of the mallard duck and its hybrid with the grey duck identified both bacteria that are potentially human pathogenic and putative novel bacteria species as determined by 16S rRNA sequencing. Significance and Impact of the Study: This study provides further evidence that duck faeces is a potential human health hazard, and has identified bacteria potentially useful for distinguishing duck faeces from other faecal sources.