bell's vireo makes a well-camouflaged nest but when found the bird will stand its ground against intruders. brown-headed cowbirds use bell's vireo nests as their own nurseries. bell's vireo often uses dense shrubbery including willows ("salix spp."), mulefat ("baccharis glutinosa"), california wild rose ("rosa californica"), mugwort ("artemisia douglasiana"), fremont cottonwood ("populus fremontii"), and western poison oak ("toxicodendron diversilobum") shrubs or vines as nesting locations.