Will Estimates of Lifetime Recruitment of Breeding Offspring on Small-Scale Study Plots Help Us to Quantify Processes Underlying Adaptation?

Reviewing 22 long-term studies of birds that provide information on the individual lifetime recruitment of breeding offspring in local study plots, we estimated local replacement rates of adults by breeding offspring (LRR) on these plots. The studies indicate that on average two thirds of the offspring emigrate to breed outside the study plots and are replaced by immigrants. Because recent studies show that individuals that disperse can differ from those that stay, and parents may produce dispersers and non-dispersers in different proportions, recruitment of breeding offspring in local study plots may not reflect the total recruitment of breeding offspring in the whole population. It is concluded that the identification of adaptations using estimates of lifetime recruitment of breeding offspring in study plots may be misleading and conclusions concerning adaptations are most often premature and extremely complicated to demonstrate quantitatively.