From gannets to seagulls, puffins to penguins, all seabirds suffer the same drop in birth rates when the supply of fish drops to less than a third of maximum capacity. That's the result from an international study on the relationships between predators and prey in seven ecosystems around the world, published in the magazine Science and coordinated by Philippe Cury, an IRD researcher. Based on nearly 450 cumulative years of observation, the research team compared the growth in fish supplies and the reproductive patterns of 14 species of coastal birds. These birds mainly feed on sardines, anchovies, herring and prawns, all of which are victims of over fishing. Below the critical level of one third of the fish biomass, the birds -- and the stability of the entire ecosystem -- come under threat.