The effects of season, sex, age and weather on population‐level variation in the timing of activity in Eurasian Blue Tits Cyanistes caeruleus

Abstract

All birds sleep and many do so in a specific location, the roost. Thus, every day each individual needs to decide when to go to (enter) and leave the roosting place. This determines the timing of activity, a trait shaped by both natural and sexual selection. Despite its importance in a variety of contexts, including foraging, predation, mating success and parental care, variation in the timing of activity has rarely been studied. Here, we describe this variation in a population of Eurasian Blue Tits Cyanistes caeruleus roosting in nestboxes using data collected over 7 years. We investigate seasonal changes in the start and end of activity and assess to what extent these parameters are sex‐ and age‐specific and affected by weather. We show that the start of activity is relatively constant in relation to sunrise during winter but undergoes drastic changes during the breeding season. The end of activity is markedly later relative to sunset in mid‐winter and is also strongly influenced by breeding behaviour. Females generally start their activity later and end it earlier than males. The duration of daily activity is shorter during periods of rain and longer when temperatures are relatively high for the time of year.

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

“…Emergence and entry times were measured during the egg laying phase (i.e., after the first egg was laid and before incubation started) and for a subset of individuals also during the pre‐egg laying phase (i.e., when nest building was completed and before the first egg was laid; see below). As individuals shift the timing of activity substantially between the different stages of breeding (Schlicht & Kempenaers, 2020), the physiological state should not differ between individuals when measuring activity patterns. During the pre‐egg laying phase, all individuals should thus be measured once nest building is completed.…”

“…Furthermore, a concern that has potentially not sufficiently been taken into account in previous studies on the fitness consequences of the daily timing of activity is the contribution of temporal variation across the breeding season as underlying driver of such relationships between fitness and timing of activity. Emergence time, entry time, and therewith active daylength, which are key parameters when studying individual variation in temporal behavior, vary throughout the year (Schlicht & Kempenaers, 2020; Steinmeyer et al, 2010; Stuber et al, 2015), even after correcting for the seasonal changes in the timing of sunrise and sunset. This suggests that the significance of sunrise and sunset for determining activity patterns may differ across the year or with date of measurement both within and among individuals.…”

Light, Sleep and Performance in Diurnal Birds

“…These findings are generally consistent with behavioral studies of blue tits (Cyanistes caeruleus). Steinmeyer et al [61] and Schlicht and Kempenaers [62] found that blue tits slept 4-5 h less in spring than in winter, based on sleep behavior and time spent in the nest box, re- [54]. There are two broad mechanisms by which these effects might occur.…”

“…These findings are generally consistent with behavioral studies of blue tits ( Cyanistes caeruleus ). Steinmeyer et al [ 61 ] and Schlicht and Kempenaers [ 62 ] found that blue tits slept 4–5 h less in spring than in winter, based on sleep behavior and time spent in the nest box, respectively. The timing of sleep also varied seasonally; in autumn and spring, blue tits usually began sleeping before sunset, whereas in winter, they began sleeping after sunset.…”

Female in-nest attendance predicts the number of ectoparasites in Darwin's finch species

“…As a corollary of this prediction, we explore factors that may be associated with longer female nest attendance (male feeds to female, male feeds to chicks, chick age). Finally, we consider an alternative explanation, namely that the date of nesting explains variation in parental care, given changes in timing of activity associated with ambient temperature [ 39 , 40 ], invertebrate abundance [ 41 ] or other factors we did not measure. We also analysed nesting date in relation to number of P. downsi per nest, as the number of parasites may increase across the host nesting season [ 42 ].…”