a, Recorded foraging ranges for seabird species that feed on smaller prey (light tone, 0.1–9 g individual wet weight) or larger prey (dark tone, 1–50 g individual wet weight; broken lines indicate that greater ranges are expected for two of the species thus foraging area calculations assumed that the foraging range is the radius of the foraging area). b, Primary production in the foraging area. c, Modelled biomass. d, Production of fauna in the foraging area. Median and 90% uncertainty intervals on the basis of 10,000 simulations to assess the effects of parameter uncertainty39 on biomass or production estimates are shown. Biomass and production were estimated for fauna in the prey size ranges consumed by each bird species, and expressed as wet and nitrogen (N) weight, respectively.