What they found was a remarkable global consistency between access to fish and seabird breeding success. Wherever they occurred in the world the effect of low fish was similar. Österblom and his colleagues found that breeding reaches a plateau and does not change even as food abundance increases. When the amount of fish in the sea was greater than one-third of maximum levels of fish, the number of chicks produced remained pretty much unaffected. But if the fish abundance fell below this one-threshold, the number of chicks produced declined. "The global pattern shows a threshold below which the numerical breeding response declines strongly as food abundance decreases," says Henrik Österblom. Österblom and his colleagues also found that breeding reaches a plateau and does not change even as food abundance increases.
- Philippe M. Cury, Ian L. Boyd, Sylvain Bonhommeau, Tycho Anker-Nilssen, Robert J.M. Crawford, Robert W. Furness, James A. Mills, Eugene J. Murphy, Henrik u00d6sterblom, Michelle Paleczny, John F. Piatt, Jean-Paul Roux, Lynne Shannon and William J. Sydeman. 2011. Global seabird response to forage fish depletion u2014 one-third for the birds. Science 334, Issue 6063.