Abstract
Shifts in reproductive phenology due to climate change have been well documented in many species but how, within the same species, other annual cycle stages (e.g. moult, migration) shift relative to the timing of breeding has rarely been studied. When stages shift at different rates, the interval between stages may change resulting in overlaps, and as each stage is energetically demanding, these overlaps may have negative fitness consequences. We used long-term data of a population of European pied flycatchers (Ficedula hypoleuca) to investigate phenological shifts in three annual cycle stages: spring migration (arrival dates), breeding (egg-laying and hatching dates) and the onset of postbreeding moult. We found different advancements in the timing of breeding compared with moult (moult advances faster) and no advancement in arrival dates. To understand these differential shifts, we explored which temperatures best explain the year-to-year variation in the timing of these stages, and show that they respond differently to temperature increases in the Netherlands, causing the intervals between arrival and breeding and between breeding and moult to decrease. Next, we tested the fitness consequences of these shortened intervals. We found no effect on clutch size, but the probability of a fledged chick to recruit increased with a shorter arrival-breeding interval (earlier breeding). Finally, mark-recapture analyses did not detect an effect of shortened intervals on adult survival. Our results suggest that the advancement of breeding allows more time for fledgling development, increasing their probability to recruit. This may incur costs to other parts of the annual cycle, but, despite the shorter intervals, there was no effect on adult survival. Our results show that to fully understand the consequences of climate change, it is necessary to look carefully at different annual cycle stages, especially for organisms with complex cycles, such as migratory birds.
Highlights
During the past decades, increases in temperature caused by global warming have affected biological systems in various ways (Walther et al, 2002)
Egg-laying dates and moult dates shifted unequally, we calculated the interval between each stage and tested whether they changed across years
Our results show that climate change affected the annual cycle stages of the European pied flycatcher, making them shift at different rates from one another
Summary
Increases in temperature caused by global warming have affected biological systems in various ways (Walther et al, 2002). Timing of flowering, breeding and migration are some of the events known to have advanced in response to the increased temperatures (Crick et al, 1997; Parmesan, 2007; Charmantier & Gienapp, 2014; Thackeray et al, 2016) Such changes make important to understand whether shifts in timing are fast enough to track changes in the optimal timing for stages to occur (Visser & Both, 2005; Visser, 2008). Many species of birds and mammals migrate, moult their plumage/pelage and/or hibernate These additional stages of the annual cycle are likewise reported to shift due to climate change (Both & te Marvelde, 2007; Ozgul et al, 2010; Charmantier & Gienapp, 2014; Morrison et al, 2015; Zimova et al, 2016). Apart from describing the changes in patterns through time, we investigated the potential environmental causes and fitness consequences of the variation in timing of these important stages
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