Abstract
Ambient temperature experienced by an animal during development or subsequently as an adult can affect many aspects of its behaviour and life-history traits. In birds, egg incubation is a vital component of reproduction and parental care. Several studies have suggested that environmental factors (such as nest microclimate) can influence the ability of incubating parents to maintain suitable conditions for embryo development. Here, we manipulated the developmental conditions of embryos through a modification of nest box thermal microclimate to investigate female incubation behaviour and its impact on offspring fitness-related traits in a wild population of the Collared Flycatcher (Ficedula albicollis). The temperature in experimental nests was increased using a heat-pack placed under the roof of a nest box, resulting in an average temperature increase of 2.5 ºC, which corresponds to projected climate change scenarios. We demonstrated that females from nests with elevated temperature spent less time in the nest box during egg incubation and had more off-bouts than females from control nests. Moreover, we found that offspring from the experimentally heated nests had larger body mass at fledging in comparison to the control ones. Our study indicates that nest microclimate during the incubation period affects female incubation behaviour and offspring quality, indicating that environmental variation in nest temperature early in ontogeny can have important and long-lasting fitness consequences.
Highlights
Climate change models predict a warmer climate and greater variability in weather components, such as temperature or rainfall, across the world in the coming decades
Every time we report on results concerning temperature measurements, we refer to the following temperature parameters named in a consistent way: ambient temperature—measured by the weather station in Visby; nest box temperature or ambient temperature in the nest—measured with an iButton placed on the nest box wall; incubation temperature—measured in the nest cup during incubation
Our manipulation of the level of temperature in the nest was successful; temperature measured inside the nest box was higher in heated compared to control nests by 2.5 °C
Summary
Climate change models predict a warmer climate and greater variability in weather components, such as temperature or rainfall, across the world in the coming decades. All previous attempts did that by directly applying thermal manipulations to the eggs, creating largely unnatural conditions that factor out female behaviour—which can be an important modulator of the in-nest thermal conditions. When it comes to the impact of increasing temperature in relation to the climate change, most previous experiments used unrealistic temperature increases, not corresponding to projected climate scenarios. Climate models predict increases in mean temperature (between 1.5 and 3 °C in the twenty-first century; Meehl et al 2000; Pachauri et al 2014; IPCC 2020) across most of the lands—a degree of heating rarely applied as thermal manipulation in bird incubation studies. We need more information on how biologically realistic increases in ambient temperature (and —changes to the overall nest thermal microclimate) could affect the incubation behaviour of females, with cascading effects on the offspring
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