Prey choice in insectivorous steppe passerines: New insights from DNA metabarcoding

Food availability plays a key role affecting almost every aspect of bird ecology, including bird population, distribution, reproduction, and behavior. Understanding the functional relationship between prey availability and insectivorous birds’ diet is important in the current scenario of habitat loss and declining of insect and bird populations. We used a fecal metabarcoding approach coupled with prey availability sampling (arthropod abundance and biomass) to test for evidence of selective foraging in a shrub-steppe passerine assemblage over the 2017–2019 breeding seasons in semi-natural steppes of central Spain. The results showed that the six bird species selected specific arthropod taxa. Heteroptera, Orthoptera, Araneae, Lepidoptera and some Coleoptera families were the main selected prey taxa, while Formicidae appeared to be avoided, suggesting that shrub-steppe passerines tend to select prey items providing essential nutrients and energy during the breeding season, while poor quality ones are neglected. Our findings highlight the utility of metabarcoding dietary data to assess prey selection patterns in insectivorous passerines and provide valuable information for the development of conservation and management programs to ensure the long-term availability of crucial food resources for shrub-steppe birds and other insectivores.