Long-lived animals may change their foraging behavior throughout their lives, as aging affects physical abilities—such as locomotion—necessitating a recalibration of the balance between energy gain and expenditure. In addition, foraging behavior may also be influenced by an individual’s ability to respond to environmental changes and by experience-based learning. However, age-related differences in foraging behavior within a population may result from selective disappearance, in which individuals with certain foraging traits die earlier, rather than from behavioral plasticity. Few studies have demonstrated age-related changes in foraging behavior driven by behavioral plasticity, and thus, it remains unclear how foraging behavior changes with age. In this study, we investigated age-related foraging behavior at both the population and individual levels in black-tailed gulls (Larus crassirostris), a long-lived species with a lifespan exceeding 20 years, at Kabushima Island, Japan. Using bio-logging data collected over 13 years, we extracted 12,460 foraging trips from movements of 298 gulls. Given that these gulls are known to forage in both distant sea areas and areas close to their breeding grounds, including inland and estuaries, and we classified them based on the habitat used during each trip: sea, coast, estuary, land. At the population level, we examined how distance per foraging trip and habitat use changed with age. A gamma regression model showed that maximum distances of foraging trips did not change with age, suggesting that foraging at sea remained energetically costly regardless of age. However, a multinomial logistic regression model revealed that older gulls used the sea less frequently and foraged more in estuaries. At the individual level, we analyzed how behavioral variation among individuals changed with age using a beta distribution. We estimated the mean and standard deviation of the proportion of trips to the sea and estuary. The results showed that individual variation in foraging behavior at sea or in estuaries increased with age. This suggests that behavioral plasticity, rather than selective disappearance, is the primary driver of age-related foraging changes. In conclusion, black-tailed gulls adjust their foraging behavior with age, reducing costly foraging at sea. This pattern arises from increased individual variation in behavior, suggesting that some individuals shift their foraging strategies to minimize energy expenditure. These findings highlight the role of behavioral plasticity in changing foraging strategies in long-lived seabirds.