Effects of the Trophic Ecology of Exotic Game Birds on Mascarenes Biodiversity: The Case of Francolinus pondicerianus in Mauritius

Game bird species were introduced to several insular systems during the 18th and 19th centuries. The Mascarenes are a relevant example of such introductions, including the grey francolin (Francolinus pondicerianus). In the case of Mauritius and Réunion Island, although this bird has been present for more than 300 years, limited information is available concerning its behavioural adaptations in insular systems, especially regarding its feeding behaviour. The first aim of this study was to describe the diet of the grey francolin, a well-established game-bird species in the Mascarenes. From this novel information, we also wish to discuss how the grey francolin can be positioned in insular food chains, and thus, its potential impact on the biodiversity of Mauritius and Réunion Island. We provide an analysis of 9115 food items, including both insects and seeds harvested from stomach contents of 13 grey francolin. The birds were harvested in Mauritius, from two distinct zones, and their stomach contents were sorted and identified using binocular magnifiers. The results revealed a total diversity of 20 seed species and 23 insect species, with a majority of exotic species. Solanum sp., Amaranthus sp. and Chamaesyce hirta were the dominant seeds, whereas insect food items were widely dominated by ant species (Pheidole megacephala, Solenopsis geminata). Important variability was observed in the composition of stomach contents, resulting in relevant amplitudes of species-diversity indicators and the animal-versus-plant ratio, throughout the 13 birds. Furthermore, the amount of certain food items was particularly high for one stomach content, whereas their global occurrence among the 13 birds was rather low, suggesting that the grey francolin has a versatile and opportunistic diet. Despite the lack of monitoring of food availability or diversity, the variation in stomach contents suggests that the diets of these generalist birds are dependent on the availability of resources in the environment.