Phenological mismatch strongly affects individual fitness but not population demography in a woodland passerine

Abstract

Summary1. Populations are shifting their phenology in response to climate change, but these shifts are often asynchronous among interacting species. Resulting phenological mismatches can drive simultaneous changes in natural selection and population demography, but the links between these interacting processes are poorly understood. 2. Here we analyse 37 years of data from an individual-based study of great tits (Parus major) in the Netherlands and use mixed-effects models to separate the within-and across-year effects of phenological mismatch between great tits and caterpillars (a key food source for developing nestlings) on components of fitness at the individual and population levels. 3. Several components of individual fitness were affected by individual mismatch (i.e. late breeding relative to the caterpillar food peak date), including the probability of doublebrooding, fledgling success, offspring recruitment probability and the number of recruits. Together these effects contributed to an overall negative relationship between relative fitness and laying dates, that is, selection for earlier laying on average. 4. Directional selection for earlier laying was stronger in years where birds bred on average later than the food peak, but was weak or absent in years where the phenology of birds and caterpillars matched (i.e. no population mismatch). 5. The mean number of fledglings per female was lower in years when population mismatch was high, in part because fewer second broods were produced. Population mismatch had a weak effect on the mean number of recruits per female, and no effect on mean adult survival, after controlling for the effects of breeding density and the quality of the autumnal beech (Fagus sylvatica) crop. 6.These findings illustrate how climate change-induced mismatch can have strong effects on the relative fitness of phenotypes within years, but weak effects on mean demographic rates across years. We discuss various general mechanisms that influence the extent of coupling between breeding phenology, selection and population dynamics in open populations subject to strong density regulation and stochasticity.

Earlier breeding, lower success: does the spatial scale of climatic conditions matter in a migratory passerine bird?

“…2012; Reed et al. 2013). Climate‐related food availability in early life may even have long‐term consequences, as it was found to affect the likelihood of fledglings to recruit into the breeding population and their future reproductive success (Reed et al.…”

Annual rhythms that underlie phenology: biological time-keeping meets environmental change

“…However, this plasticity is limited by the complex mechanisms of avian reproduction, so that their breeding season is progressively delayed with respect to the food peak [84]. Although evidence for large effects on recruitment rates and population density is still scarce, mismatched timing of reproduction has imposed energetic and fitness consequences, including reduced fledging rate, fledging mass and adult survival [90,91].…”

No phenotypic plasticity in nest-site selection in response to extreme flooding events

“…individuals can 'overshoot' optimal conditions [15][16][17]. ECEs are often considered unpredictable in the biological literature, but it is possible that ECEs may simply be rare rather than unpredictable [10].…”