Predicting the consequences of carry-over effects for migratory populations

Abstract

Migratory animals present a unique challenge for predicting population size because they are influenced by events in multiple stages of the annual cycle that are separated by large geographic distances. Here, we develop a model that incorporates non-fatal carry-over effects to predict changes in population size and show how this can be integrated with predictive models of habitat loss and deterioration. Examples from Barn swallows, Greater snow geese and American redstarts show how carry-over effects can be estimated and integrated into the model. Incorporation of carry-over effects should increase the predictive power of models. However, the challenge for developing accurate predictions rests both on the ability to estimate parameters from multiple stages of the annual cycle and to understand how events between these periods interact to influence individual success.

Prolonged stopover and consequences of migratory strategy on local-scale movements within a regional songbird staging area

“…Stopover resources can influence migratory pace (Wikelski et al 2003(Wikelski et al ,Åkesson et al 2012, energetic condition (Moore et al 1995), and condition in subsequent life stages Moore 2005, Norris andTaylor 2006). Stopover areas that support large concentrations of birds in making flights over ecological barriers are particularly important and represent ecological bottlenecks where localized habitat loss can have population-level consequences (Myers 1983, Warnock 2010.…”

Carry-over effects, sequential density dependence and the dynamics of populations in a seasonal environment

“…For example, observational and experimental evidence in both resident and migratory animals suggest that events that induce individual variation in physiological condition during the non-breeding period can explain a significant amount of individual variation in the timing and success of reproduction the following breeding period [13][14][15][16][17]. Despite the fact that several studies on both resident and migratory animals provide evidence that COEs can shape individual fitness [13,15 -18], and that theoretical models suggest that they can interact with sequential density dependence to influence population dynamics [4,11,19], there is no empirical evidence that COEs influence per capita rates or have an effect at the population level.…”

Manipulating individual state during migration provides evidence for carry-over effects modulated by environmental conditions

“…events occurring in one season that produce residual effects on individuals the following seasons, can have large impacts on the population dynamics of migrants (see [4]). COEs are considered both from a theoretical and empirical perspective as crucial issues for a better understanding and modelling of a population's dynamic [4,6,7].…”