The anatomy of a phenological mismatch: interacting consumer demand and resource characteristics determine the consequences of mismatching

Climate change has caused shifts in seasonally recurring biological events and the temporal decoupling of consumer-resource pairs - i.e., phenological mismatching (hereafter, mismatching). Despite the hypothetical risk mismatching poses to consumers, it does not invariably lead to individual- or population-level effects. This may stem from how mismatches are typically defined, where an individual or population are matched or mismatched based on the degree of asynchrony with a resource pulse. However, because both resource availability and consumer demands change over time, this categorical definition can obscure within- or among-individual fitness effects. We investigated the effects of resource characteristics on the growth, daily survival, and fledging rates of Hudsonian godwit (Limosa haemastica) chicks hatched near Beluga River, Alaska. To do this, we developed models to identify the effects of resource characteristics on individual- and population-level processes and determine how the strength of these effects change throughout a consumers early development. We found that at the individual-level, chick growth and survival improved following periods of higher invertebrate abundance but were increasingly dependent on the availability of larger prey as chicks aged. At the population level, seasonal fledging rates were best explained by a model including age-structured consumer demand. Our study suggests that modelling the effects of mismatching as a disrupted interaction between consumers and their resources provides a biological mechanism for how mismatching occurs and clarifies when it matters to individuals and populations. Given the variable responses to mismatching exhibited by consumer populations, such tools for predicting how populations may respond under future climatic conditions will be critical for conservation planning.