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

Climate change has caused shifts in seasonally recurring biological events and the decoupling of consume-resource pairs in time – that is ‘mismatching’. Despite its theorized risks, empirical evidence for the fitness consequences of mismatching has been mixed and our understanding of when mismatching matters for populations is still rudimentary. Studies typically categorize consumers as ‘matched’ or ‘mismatched’ from the synchrony between the timing of a single life-history event and peak resource availability. However, because resource availability and consumer demands vary throughout the interaction, the synchrony definition could obscure the cumulative effects of mismatching and mask population-level consequences. Clarifying the consequences of mismatching may therefore require a more robust and mechanistic definition of mismatching. We developed models to identify the effects of resource characteristics on individual- and population-level fitness and how these change throughout the consumer’s ontogeny. From these, we estimated the effects of resource characteristics on the growth, daily survival, and fledging rates of Hudsonian godwit chicks (Limosa haemastica) hatched near Beluga River, Alaska. Godwit chicks’ growth and survival improved following periods of higher invertebrate abundance but was increasingly dependent on the availability of larger prey as they aged. At the population, seasonal fledging rates were best explained by a model with accurate of estimates consumer demand throughout ontogeny. Our study suggests that quantifying the strength of selection from resource characteristics can capture the effects of mismatching at both the individual- and population-level. Additionally, we show that consumer ontogeny affects the consequences of the mismatch over the course of the interaction because of increasing demands. Prevailing evidence for variable responses to mismatching means that tools for monitoring extinction risks will be invaluable. Replacing the synchrony definition of mismatching may be a first key step to clarifying when mismatches affect consumer populations.