Worldwide, mistletoes act as a keystone resource, providing food (nectar, fruit and foliage) and structural (nesting sites) resources to hundreds of fauna species. In Australia, loranthaceous mistletoes depend on birds for pollination and dispersal, and provide important nectar and fruit resources to a large number of nectarivorous and frugivorous species of bird. We investigated whether avian species richness and community structure varies with flowering and fruiting of two common mistletoe species (Loranthaceae : Wireleaf Mistletoe, Amyema preissii; and Box Mistletoe, A. miquelii), conducting monthly surveys of both birds and mistletoes over 1 year at five sites in south-western Western Australia (WA). Flowering and fruiting periods were distinct and differed both among sites and between mistletoe species. Nectar and ripe fruit were available for up to 5 months (Box Mistletoe) or 6–7 months (Wireleaf Mistletoe) at individual sites, but were available every month of the year across all sites. The presence of fruiting, but not flowering, mistletoe was associated with changes in bird community structure. Mistletoebirds (Dicaeum hirundinaceum) were significantly more likely to be recorded during months when ripe mistletoe fruit was present and the overall bird species richness was higher for these survey months. Mistletoes provide important resources, but further investigation is required to assess whether they act as a keystone resource in south-western WA. ; Kathryn R. Napier, Suzanne H. Mather, Todd J. McWhorter and Patricia A. Fleming