Discards from fisheries are the most important predictable anthropogenic food subsidies (PAFS) that are being incorporated into marine ecosystems. Changes on their availability and predictability can help to understand the role that food availability (i.e. an important indicator of the carrying capacity and the individual fitness) plays at different ecological levels, from individual fitness to community dynamic and ecosystem’s functioning. Seabirds constitute an excellent model to evaluate the ecological effects derived from a lack of discards for several reasons: seabirds are 1) one of the most important discard scavengers, 2) easy to monitor and 3) apical predators globally distributed, which makes them suitable ecosystem’s health indicators. Here we review the existing information on seabirds-discards interactions to identify main knowledge gaps and to propose new challenges to improve our understanding on the general role of food availability. We conclude that the new policies on the ban of fishery discards that are being progressively implemented at the European Union, Norway, Chile or New Zealand offer a suitable experimental scenario to improve our understanding on how a large decrease in the carrying capacity may alter demographic parameters such as survival, dispersal and reproduction, the resilience of populations against perturbations as well as the role of individual foraging specialization processes.