BACKGROUND: The detection of predator chemical cues is an important antipredatory behaviour as it allows an early assessment of predation risk without encountering the predator and therefore increases survival. For instance, since chemical cues are often by-products of metabolism, olfaction may gather information not only on the identity but also about the diet of predators in the vicinity. Knowledge of the role of olfaction in the interactions of birds with their environment, in contexts as important as predator avoidance, is still scarce. We conducted two two-choice experiments to explore 1) whether the house finch Carpodacus mexicanus can detect the chemical cues of a marsupial predatory mammal, the common opossum (Didelphis marsupialis), and 2) whether its response to such cues is influenced by the recent diet of this omnivorous predator, as this would increase the accuracy with which the risk of predation is assessed. RESULTS: House finches avoided the area of the apparatus containing the scent of the predator, and this effect did not depend on the recent diet (bait used to lace the traps) of the predator. CONCLUSIONS: Our results provide clear evidence that house finches detect and use the chemical cues of predators to assess the level of predation risk of an area and avoid it.