The influence of meal size on prey DNA detectability in piscivorous birds

Molecular methods allow non-invasive assessment of vertebrate predator-prey systems at high taxonomic resolution by examining dietary samples such as faeces and pellets. To facilitate the interpretation of field-derived data, feeding trials, investigating the impacts of biological, methodological, and environmental factors on prey DNA detection have been conducted. The effect of meal size, however, has not yet been explicitly considered for vertebrate consumers. Moreover, different non-invasively obtained sample types remain to be compared in such experiments. Here, we present a feeding trial on abundant piscivorous birds, Great Cormorants (Phalacrocorax carbo), to assess meal size effects on post-feeding prey DNA detection success. Faeces and pellets were sampled twice a day after the feed of large (350-540 g), medium (190-345 g), and small (15-170 g) fish meals contributing either a large (>79%) or small (<38%) share to the daily consumption. Samples were examined for prey DNA a...