Residency and site fidelity of marked populations of the nectar-feeding common blossom bat Syconycteris australis were monitored for three years in three areas of high food availability (density of Banksia integrifolia inflorescences) and three of low food availability on the north coast of New South Wales, Australia. Resident bats were present in all sites; however, populations in areas with low food abundance were more likely to be resident (63% recaptured) over a six-month flowering season than populations in areas with high food abundance (20% recaptured). Residents were more likely to be adult males, than females or juveniles. Intruder pressure fluctuated throughout the year with food abundance as the number of transients was correlated with the density of inflorescences. This had a marked effect on bats in autumn, when a lower percentage of residents than transients was reproductive in sites with high intruder pressure. Also, residents at sites with high intruder pressure were less likely to be reproductive and their body condition was lower than residents experiencing low intruder pressure. Thus intruder pressure was probably the most important factor reducing residency. Nectar and pollen was locally scarce after B. integrifolia finished flowering; however, many bats returned to the same site in the following year. Site fidelity between consecutive B. integrifolia flowering seasons (years), was greater in low-food sites (28%) than areas of high food (12%). The proximity of non B. integrifolia food sources may contribute to the degree of site fidelity, but this is yet to be tested. One site was monitored for five consecutive years and at least 4% of those marked in the first year were site faithful after five years. Strong site attachment would increase the vulnerability of this species to the effects of disturbance. These observations indicate that the abundance and dispersion of food has an important influence on behaviour and population dynamics of S. australis over long periods.