Territorial behaviour is widespread among insects and serves as an important constituent of male reproductive success. In butterflies, competition for perching sites is mediated through aerial persistence duels in which the mechanisms of resolution have remained obscure. There is evidence in some species for an effect of age upon contest outcome, which could arise due to individuals adopting lifetime strategies of reproductive risk taking, or as a consequence of lifetime changes in resource-holding potential (RHP). RHP in territorial insects is often equated to the ability for sustained or high-performance flight, and if the morphological and/or energetic determinants of flight performance vary with age then this may explain putative age effects. I addressed this possibility by charting the correlates of residency in two nymphalid species, Hypolimnas bolina L. and Melanitis leda L., at popular perching sites in tropical Australia. Among samples of 55 male H. bolina (20 residents paired to 35 non-residents) and 36 male M. leda (13 residents paired to 23 non-residents), I found moderately sized relationships (effect sizes, d = 0.46-0.79) between residency and the studied biophysical variables (body size, absolute and relative lipid stores, and relative flight musculature). However, differences in age were always much larger (effect sizes, d = 1.23-1.52), with old male H. bolina and young male M. leda favoured for residency. The most parsimonious logistic model of residency in each case proved to be the model containing age only; hence, this study supports the notion of primarily age-based competitive strategies in these two butterflies.