Insectivorous bats are known to consume arthropods from several orders, and have a significant impact on agricultural ecosystems by reducing crop pests. However, information is still lacking about geographic and seasonal variation in diet. Although studies of Mexican free-tailed bats (Tadarida brasiliensis mexicana) in Texas demonstrate the importance of this species on agricultural pests like the corn earworm (Helicoverpa zea), less is known about the diet of the species towards the edge of its range. This study investigates the dietary preferences of bats by analyzing genomic information found in their guano. We examined the diet of T. b. mexicana in Butte County, California by collecting guano from 20 bat houses during the winter of 2020-2021 and used DNA metabarcoding to identify prey. Thirty-one species, twenty-seven families and eleven orders were identified, with Diptera representing 54% of all reads. Although Coleoptera (22%) and Hemiptera (11%) were also common, Lepidoptera only accounted for 8% of their winter diet. The most common species in the diet were moth flies (Psychoda albipennis), ground beetles (Tanystoma cuyama) and pine-needle aphids (Essigella californica). We plan to continue this study throughout an entire year to examine seasonal variation in diet.