Interspecific competition and age structure key to predicting population fluctuations.
Understanding how different bird species coexist by competing for resources was studied. Great tits and blue tits were monitored in Europe, showing that both species are similarly affected by competition. Great tits mainly compete within their own species, while blue tits also compete with the other species. Age plays a role in how well they compete. Including age-specific competition effects in models helps predict population size changes better.