No relationship between chronotype and timing of breeding when variation in daily activity patterns across the breeding season is taken into account

Abstract

There is increasing evidence that individuals are consistent in the timing of their daily activities, and that individual variation in temporal behavior is related to the timing of reproduction. However, it remains unclear whether observed patterns relate to the timing of the onset of activity or whether an early onset of activity extends the time that is available for foraging. This may then again facilitate reproduction. Furthermore, the timing of activity onset and offset may vary across the breeding season, which may complicate studying the above‐mentioned relationships. Here, we examined in a wild population of great tits (Parus major) whether an early clutch initiation date may be related to an early onset of activity and/or to longer active daylengths. We also investigated how these parameters are affected by the date of measurement. To test these hypotheses, we measured emergence and entry time from/into the nest box as proxies for activity onset and offset in females during the egg laying phase. We then determined active daylength. Both emergence time and active daylength were related to clutch initiation date. However, a more detailed analysis showed that the timing of activities with respect to sunrise and sunset varied throughout the breeding season both within and among individuals. The observed positive relationships are hence potentially statistical artifacts. After methodologically correcting for this date effect, by using data from the pre‐egg laying phase, where all individuals were measured on the same days, neither of the relationships remained significant. Taking methodological pitfalls and temporal variation into account may hence be crucial for understanding the significance of chronotypes.

Reproductive fitness is associated with female chronotype in a songbird

“…Our study is among the few that have identified fitness correlates of (relative) chronotype in female animals. We firstly show high repeatability of timing, and thus corroborate evidence of chronotype as a consistent individual trait in birds, including in our study species (Graham et al, 2017; Meijdam et al, 2022; Stuber et al, 2015). We then show that the relative chronotype of female great tits, measured during the incubation period, predicted reproductive success, such that early-rising females raised more offspring to fledging than late (relative) chronotypes.…”

“…In this study, we leverage data from wild birds to i) disentangle factors that contribute to explain variation in clock and relative chronotype, and ii) newly document links between chronotype and reproductive success. Here, we examine a well-studied songbird whose chronotype has been shown to be repeatable, the great tit ( Parus major; Graham et al, 2017; Meijdam et al, 2022; Stuber et al, 2015). We inferred female chronotype through measuring behaviour during incubation, a critically important post-zygotic stage of avian reproduction, while monitoring reproductive success (Capilla-Lasheras, 2018; Graham et al, 2017; Gwinner et al, 2018; Maury et al, 2020).…”

Intrinsic individual variation in daily activity onset and plastic responses on temporal but not spatial scales in female great tits

“…From the total of 1076 observations 5 datapoints were collected using the infrared cameras (1 in 2018, 4 in 2021), 49 using the RFID loggers (9 in 2018, 40 in 2020) and all remaining data via SongMeters (see also 39 for more details on the data selection process). We removed one datapoint from the dataset as it was an outlier.…”