Data from: Accounting for interspecific competition and age structure in demographic analyses of density dependence improves predictions of fluctuations in population size

Understanding species coexistence has long been a major goal of ecology.
Coexistence theory for two competing species posits that intraspecific
density dependence should be stronger than interspecific density
dependence. Great tits and blue tits are two bird species that compete for
food resources and nesting cavities. Based on long-term monitoring of
these two competing species at sites across Europe, combining
observational and manipulative approaches, we show that the strength of
density regulation is similar for both species, and that individuals have
contrasting abilities to compete depending on their age. For great tits,
density regulation is driven mainly by intraspecific competition. In
contrast, for blue tits, interspecific competition contributes as much as
intraspecific competition, consistent with asymmetric competition between
the two species. In addition, including age-specific effects of intra- and
interspecific competition in density-dependence models improves
predictions of fluctuations in population size by up to three times.