Fig. 3. Three levels of cross-seasonal nonbreeding influences upon population dynamics of seasonal migrants, illustrating the required nonbreeding characteristic, the subsequent season impact, and the consequences for population growth; linear relationships are assumed for simplicity, and each level is presented independently from others (i.e., without accounting for potential interactions among levels). At the individual level, carry-over of individual condition or migration timing from one season to another can result in short-term positive correlations among seasonal vital rates and between nonbreeding vital rates and population growth. At the population level, density-dependence in one season can cause negative relationships between seasonal vital rates which may buffer overall effects on population growth. At the environmental level, broad-scale climatic trends can cause positive covariation among seasonal environments and thus among consecutive seasonal vital rates, with the potential for magnified climatic impacts on population growth. See Table 2 and text for further details and literature examples.