Correlations between sequential timing decisions do not necessarily indicate strategic behavior: a comment on Bêty et al

Abstract

Using correlation analysis, Bêty, Gauthier, and Giroux confirmed that individuals of the migrating snow geese (Chen caerulescens atlantica) arriving earlier on their breeding grounds experienced longer prelaying periods but laid earlier than late-arriving birds. They concluded that these birds strategically adjusted timing to optimize fitness. This test is, however, not sufficient to indicate strategic behavior. We show analytically that, without assuming strategic behavior, arrival date, prelaying period, and laying date are correlated with each other because of their sequential occurrence. We conclude that correlation tests on sequentially occurring variables are not sufficient to detect nonrandom relations.