On a small island off south-western Australia, tiger snakes (Notechis scutatus, Elapidae) continue to survive, feed, grow and reproduce successfully after being blinded by seagulls defending their chicks. We propose two alternative hypotheses to explain this surprising result: either vision is of trivial importance in tiger snake foraging, or the blinded snakes survive on a diet of abundant immobile prey that cannot escape their approach. Laboratory studies in which we blindfolded snakes falsified the first hypothesis: snakes that were unable to see had great difficulty in capturing mobile prey. Field data support the second hypothesis: blind snakes feed almost entirely on seagull chicks, whereas normal-sighted animals also took fast-moving prey (lizards and mice). Thus, the ability of tiger snakes on Carnac Island to survive without vision is attributable to the availability of abundant helpless prey (seagull chicks) in this insular ecosystem.