THE DIET OF A THREATENED PASSERINE USING METABARCODING: THE BLACK WHEATEAR (Oenanthe leucura)

THE DIET OF A THREATENED PASSERINE USING METABARCODING: THE BLACK WHEATEAR (Oenanthe leucura)

Luis Pascoal da Silva (CIBIO-InBIO) | March 3, 2019 | X Congresso de Ornitologia da SPEA, Peniche, Portugal

The Black wheatear (Oenanthe leucura) is the most threatened resident passerine in Portugal. In our country it occurs mainly in anthropogenic habitats, as the Alto Douro vineyards. Studies on the diet of this species are old and are mainly from the desert regions of southern Spain. The aims of this work were not only to describe in detail the diet of the Black wheatear in Portugal, but also to evaluate the advantages and pitfalls of using genetic molecular tools, metabarcoding, to study the diet of passerines. In this study we used genetic identification, of 115 bird droppings using 4 molecular markers. The method allowed the description of the diet with an unpreceded detail. However, there were several problems associated with the technique, namely the bias of some molecular primers towards some taxonomic groups and the detection of secondary predation. The diet of the Black wheatear is extremely wide, with the presence of reptiles, numerous orders of invertebrates and several plant species. The animal component of the Black wheatear diet is dominated by Hymenoptera, mainly ants, while fruit ingestion is also very common, especially of ruderal plants. The results did not suggest the occurrence of dietary differences between adult and juvenile birds, but revealed a partition between males and females. Females tended to have a higher preference for ants than males. The use of metabarcoding for the study of passerines diet has revealed as a very powerful tool, presenting an unprecedented taxonomic resolution. However, this methodology showed several challenges and caveats that need special attention when analyzing the raw data. Our results describe also for the first time intraspecific niche partitioning in Black wheatears. The acquired knowledge brings a new understanding of the ecological requests of this critically endangered species, allowing a more efficient monitoring and conservation.