Theory and limited evidence suggest that species interactions within local communities can turnover more quickly than the species composition across environmental gradients. However, relatively few studies have tested for this possibility. Here, we studied how the composition of arthropods species consumed by birds varied across a gradient of land use intensity in southern Costa Rica. We used constant-effort mist net sampling in 24 sites spanning intact forest reserves to intensive coffee plantations to record bird species composition and collect fecal samples for dietary analysis. We then used DNA metabarcoding to estimate the consumption of arthropod prey in the fecal samples in different land use types. In total, we collected approximately 1700 fecal samples from 160 bird species across the land use intensity gradient.
Changes in the composition of consumed arthropods across the sites were affected by the interaction between habitat type and bird species identity. This result suggests that some bird species may have expanded dietary breadth to make use of resources available in modified habitats. In addition, we found that the richness of arthropod species consumed increased with land use intensity, with the highest level observed in sites where diversified agriculture was practiced, and then dropped sharply in sites that had the most intensive land use, i.e., monoculture coffee. These changes may have been caused by an increase in habitat heterogeneity at low-to-moderate levels of land use intensity. Overall, our results suggest that habitat modification may have restructured trophic interactions between arthropods and birds in this countryside landscape.