Aurelia F. T. Strauß’s research while affiliated with University of Groningen and other places

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Publications (4)


Circadian clock period length is not consistently linked to chronotype in a wild songbird
  • Article

September 2024

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30 Reads

European Journal of Neuroscience

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Aurelia F T Strauß

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[...]

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Circadian clock properties vary between individuals and relate to variation in entrained timing in captivity. How this variation translates into behavioural differences in natural settings, however, is poorly understood. Here, we tested in great tits whether variation in the free‐running period length ( tau ) under constant dim light (LL) was linked to the phase angle of the entrained rhythm (“chronotype”) in captivity and in the wild, as recently indicated in our study species. We also assessed links between tau and the timing of first activity onset and offset under LL relative to the last experienced light–dark (LD) cycle. We kept 66 great tits, caught in two winters, in LL for 14 days and subsequently released them with a radio transmitter back to the wild, where their activity and body temperature rhythms were tracked for 1 to 22 days. For a subset of birds, chronotype was also recorded in the lab before release. Neither wild nor lab chronotypes were related to tau . We also found no correlation between lab and wild chronotypes. However, the first onset in LL had a positive relationship with tau , but only in males. Our results demonstrate that links between tau and phase of entrainment, postulated on theoretical grounds, may not consistently hold under natural conditions, possibly due to strong masking. This calls for more holistic research on how the many components of the circadian system interact with the environment to shape timing in the wild. Wild birds showed chronotypes in the field that were unlinked to their circadian period length tau measured in captivity. In males only, the first onset of activity after exposure to constant dim light did correlate with tau . Our study emphasises the need to investigate clocks in the real world, including a need to better understand masking.


Variation in diel timing in great tits is affected by the timing of their social mate
  • Preprint
  • File available

August 2024

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54 Reads

Diel rhythms are driven by genetic and environmental components. These rhythms are mediated by the circadian clock, and entail rhythmicity of various physiological and behavioural traits. Although individuals show to some extent repeatable timing (i.e., chronotype), there is ample variation of diel timing observed within and between individuals of the same species. Here, we investigated various environmental factors, including timing of the social partner, that could explain day-to-day variation within individuals. Synchronisation with the social partner during provisioning timing could increase breeding success, and decrease extrapair paternity opportunities for females during the fertile period in case of consistent timing across the breeding stages. Therefore, we also investigated fitness consequences of between-individual variation. We first assessed the magnitude of between- and within-individual variation in the timing of nest visits by great tits ( Parus major ). We monitored nest visits of males and females in 37 broods during chick provisioning in 2020 and 2021. Next, we explored the responsiveness of the diel timing to environmental variables, specifically comparing abiotic and social factors. The onset of nest visits varied significantly with day within the breeding season, rainfall and the diel timing of the breeding partner but not with night temperature. In response to the partner’s onset, females responded stronger compared to males. By contrast, offset was generally more variable within individuals and less variation was explained by the environmental variables. Both males and females delayed their activity offset with the progressing season and females also had a later onset with more daytime rainfall. Further, the reproductive output and extrapair paternity were independent of parental chronotype and their synchronisation within pairs. It is possible that consistency of chronotypes is less important for reproductive success than the ability to plastically respond to changing environmental conditions. Thus, the next step could be to investigate potential individual differences in plasticity which could be even linked to specific chronotypes. This information might be crucial to predict how species can cope with unpredictable environmental conditions.

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Short-time exposure to light at night affects incubation patterns and correlates with subsequent body weight in great tits (Parus major)

February 2024

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100 Reads

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3 Citations

Journal of Experimental Zoology Part A Ecological and Integrative Physiology

Artificial light at night (ALAN) widely affects wildlife by blurring light‐dark differences, including transitions such as sunrise and sunset, thereby affecting regulation of diel rhythms. As a result, activity onsets in many wild diurnal songbirds advance under ALAN. From chronobiological studies, it is known that the direction and strength of the response to light depends on when during the night exposure takes place. However, these experiments are mostly done under continuous light conditions, when animals have free‐running rhythms. It remains unclear whether phase‐dependence also holds in entrained, wild songbirds; i.e., does the effect of ALAN on activity patterns differ between exposure in the morning compared to the evening? This information is essential to assess the effects of mitigation measures by limiting ALAN to selected times of the night. We exposed incubating great tits ( Parus major ) inside the nest‐box to 4 h of dim light, of which 1 h overlapped with dawn before sunrise or dusk after sunset. We found a small advancing effect of morning‐light on activity onset and of evening‐light on offset compared to dark controls but not vice versa . Breeding success and chick condition were unaffected by the light treatments. However, light‐treated females had lower weights 9–18 days after the end of the treatment compared to the controls, independent of whether ALAN occurred in the morning or the evening, indicating possible costs of ALAN. Despite the weak behavioral response, ALAN might have affected the females' circadian clock or physiology resulting in lower body condition.


Time profile of ambient temperature, and rhythmicity of skin temperature and activity. Upper three panels show time profiles of ambient temperature (A), skin temperature (B) and activity (C) (10-min binned) against date and time for an exemplary Great Tit (frequency 173.204, male) kept in an outdoor aviary during winter. Bottom two panels show corresponding autocorrelation plots for skin temperature (D) and activity (E), including a red vertical line to indicate 24 h
Diel profiles for skin temperature (A) and activity (B) for each individual Great Tit (unsmoothed data in different colours) and mean (black solid curves) ± standard error (black dashed curves) for the full data set. Blue curve shows the fitted sinusoidal curve (with 3 harmonics) for skin temperature. Horizontal red lines show overall mean (levels). Daylight phases are indicated in yellow (sunrise–sunset)
Bird-specific skin temperature profiles, centred around minima and maxima to estimate onset and offset. Shown skin temperature curves for onset (A) and offset (B) are smoothed with 1 (red, dashed) and 3 (blue, solid) harmonics. Graphs also show means (black dots) ± standard error (grey bars) per 10-min bin. Daylight phases are indicated in yellow (sunrise–sunset). Sex: female (F) and male (M))
Determination of onset and offset of diel change in skin temperature. Bird-specific onset (A) and offset (B) estimates are calculated by four methods (different colours) for eight Great Tits (female (F) and male (M)) kept in outdoor aviaries during winter. Mean (± SEM) chronotype estimates (in numeric daytime hours) and information on colour coding are given for each method in the inlay. Each panel represents skin temperatures of one Great Tit with mean (black dots) ± standard errors (grey bars) per 10-min bin, the fitted sinusoidal curve (blue, based on 3-harmonic smoothing), and the skin temperature chronotype estimates as vertical lines. Daylight phases are indicated in yellow (sunrise–sunset)
Individual chronotype estimates based on individually averaged diel patterns of skin temperature and activity. Colours indicate different analytic methods for skin temperature, estimates for activity chronotype are shown as black diamonds. Great Tits (female (F) and male (M)) are ranked by activity onset. Daylight phases are indicated in yellow (sunrise–sunset)
Using skin temperature and activity profiles to assign chronotype in birds

September 2022

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173 Reads

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3 Citations

Animal Biotelemetry

Chronotypes describe consistent differences between individuals in biological time-keeping. They have been linked both with underlying variation in the circadian system and fitness. Quantification of chronotypes is usually by time of onset, midpoint, or offset of a rhythmic behaviour or physiological process. However, diel activity patterns respond flexibly to many short-term environmental influences, which can make chronotypes hard to identify. In contrast, rhythmic patterns in physiological processes, such as body temperature, may provide more robust insights into the circadian basis of chronotypes. These can be telemetrically recorded from skin-mounted, temperature-sensitive transmitters, offering minimally invasive opportunities for working on free-ranging animals in the wild. Currently, computational methods for deriving chronotype from skin temperature require further development, as time series are often noisy and incomplete. Here, we investigate such methods using simultaneous radio telemetry recordings of activity and skin temperature in a wild songbird model (Great Tit Parus major) temporarily kept in outdoor aviaries. Our aims were to first develop standardised selection criteria to filter noisy time series of skin temperature and activity, to second assign chronotype based on the filtered recordings, and to third compare chronotype as assigned based on each of the two rhythms. After the selection of rhythmic data using periodicity and autocorrelation parameters, chronotype estimates (onset and offset) were extracted using four different changepoint approaches for skin temperature and one approach for activity records. The estimates based on skin temperature varied between different approaches but were correlated to each other (onset: correlation coefficient r = 0.099–0.841, offset: r = 0.131–0.906). In contrast, chronotype estimates from skin temperature were more weakly correlated to those from activity (onset: r = −0.131–0.612, offset: r = −0.040– −0.681). Overall, chronotype estimates were less variable and timed later in the day for activity than for skin temperature. The distinctions between physiological and behavioural chronotypes in this study might reflect differences in underlying mechanisms and in responsiveness to external and internal cues. Thus, studying each of these rhythms has specific strengths, while parallel studies of both could inform broadly on natural variation in biological time-keeping, and may allow assessment of how biological rhythms relate to changes in the environment.

Citations (1)


... The ability to collect repeated activity measures consistently from the same individual across an extended period is limited by technology. Previous descriptions of activity in wild birds have varied between different tracking methods including radiofrequency tracking with the use of passive integrated transponder tags, radio transmitters that give an indication of proximity of a bird to a receiver, sound recordings at a nestbox, ibutton temperature recordings within a nest cup, and recently, internal body temperature (Strauß et al. 2022). Each method has advantages and disadvantages, for example radio transmitters track activity on individuals only within range of an antennae and ibutton temperature data can only be collected when an individual is regularly in contact with the logger such as during incubation of eggs. ...

Reference:

Daily activity is repeatable but varies across the breeding season in female great tits
Using skin temperature and activity profiles to assign chronotype in birds

Animal Biotelemetry