After Humboldt, Xerónimo went on to work for California Audubon.

  For his thesis, Xerónimo studied barn owl habitat use within a vineyard agroecosystem by quantifying the extent of time barn owls spend hunting within vineyards versus adjacent habitats. He also collected data on the owls’ efficiency in removing rodent pests from the landscape. Xerónimo compiled these data to better understand the potential for barn owls to provide regulating services to viticulturists in one of the world’s most well-known wine regions, Napa Valley.