Phenological indices of avian reproduction: cryptic shifts and prediction across large spatial and temporal scales

Abstract

Climate change-induced shifts in phenology have important demographic consequences, and are frequently used to assess species' sensitivity to climate change. Therefore, developing accurate phenological predictions is an important step in modeling species' responses to climate change. The ability of such phenological models to predict effects at larger spatial and temporal scales has rarely been assessed. It is also not clear whether the most frequently used phenological index, namely the average date of a phenological event across a population, adequately captures phenological shifts in the distribution of events across the season. We use the long-tailed tit Aegithalos caudatus (Fig. 1) as a case study to explore these issues. We use an intensive 17-year local study to model mean breeding date and test the capacity of this local model to predict phenology at larger spatial and temporal scales. We assess whether local models of breeding initiation, termination, and renesting reveal phenological shifts and responses to climate not detected by a standard phenological index, that is, population average lay date. These models take predation timing/intensity into account. The locally-derived model performs well at predicting phenology at the national scale over several decades, at both high and low temperatures. In the local model, a trend toward warmer Aprils is associated with a significant advance in termination dates, probably in response to phenological shifts in food supply. This results in a 33% reduction in breeding season length over 17 years – a substantial loss of reproductive opportunity that is not detected by the index of population average lay date. We show that standard phenological indices can fail to detect patterns indicative of negative climatic effects, potentially biasing assessments of species' vulnerability to climate change. More positively, we demonstrate the potential of detailed local studies for developing broader-scale predictive models of future phenological shifts.

Energetics of communal roosting in chestnut-crowned babblers: implications for group dynamics and breeding phenology

“…Like babblers, they show seasonal fissionfusion social dynamics. Compared with chestnut-crowned babblers, long-tailed tit flocks fragment more synchronously into breeding pairs, but as we have suggested for babblers, the timing of fragmentation and breeding phenology are strongly temperature dependent (Gullett et al, 2013). More broadly, the concept that energy costs of solitary roosting might act as a significant selection pressure on social dynamics and breeding phenology may be relevant to many social species.…”

Individual fitness and the effects of a changing climate on the cessation and length of the breeding period using a 34‐year study of a temperate songbird

“…In contrast, a study focused only on the initiation of breeding in song sparrows suggests an earlier start to breeding and an increase in fecundity (Essak, ; Germain, Wolak, Arcese, Losdat, & Reid, ), given that warmer spring temperatures result in earlier initiation of breeding (Wilson & Arcese, ). These contrasting results suggest complexity in predicting how climate will affect fitness (e.g., Gullett et al., ; Husby et al., ; Jankowiak & Wysocki, ; Matthysen et al., ; Mcdermott & Degroote, ; Moller et al., ). Because many other long‐term studies have examined factors affecting the initiation of breeding, our current results could be relatively easily replicated to ask in other species how multiple abiotic factors influence breeding phenology and fitness, potentially allowing generalizations based on species traits.…”

Helping in cooperatively breeding long-tailed tits: a test of Hamilton's rule

“…The end of the breeding season varies between years according to April temperature [80], so we analysed renesting decisions relative to a standardized breeding termination date for ease of comparison across years. The dataset comprised information for 377 males involved in 868 breeding attempts.…”