In 2004–05, we evaluated seasonal variation in the diet of White-tailed Kites in a suburban area of Concepción, southern Chile. Kites' diet was determined based on pellets (N  =  209) and consisted of rodents, insects and birds (95.6%, 13.8% and 0.6% of all consumed individual prey [N  =  343]). Olivaceous field mice (Abrothrix olivaceus) and long-haired mice (A. longipilis) were the most common prey (47.5% and 32.4% of all prey by frequency, respectively; 40.3% and 38.9% by biomass, respectively). Rodents were important in the diet in all seasons (frequency  =  88.6–100%, biomass  =  98.8–100%), and the ranking of rodent prey species in the diet was virtually the same for all seasons (χ²  =  4.6, P > 0.05). The geometric mean weight of vertebrate prey was also similar among seasons (27.0–28.6 g). The frequency of rodent prey species in the pellets was positively correlated to rodent prey abundance in the environment, as measured using live-trapping surveys (r_s  =  0.83, P < 0.05). Our results corroborate previous findings that the White-tailed Kite is a rodent-specialist predator and suggest that in our study area it behaves as an opportunistic predator (i.e., capturing rodent prey in proportion to their availability).