Data from: Chronotype and seasonal timing of reproduction are related in a female songbird
Data files
Jul 07, 2026 version files 120.46 KB
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ActivityChicks.csv
19.51 KB
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ActivityIncubation.csv
25.95 KB
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ActivityLaying.csv
15.61 KB
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ActivityPrebreeding.csv
27 KB
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ActivityPrebreedingInd.csv
28.82 KB
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README.md
3.56 KB
Abstract
Seasonally breeding animals depend on local environmental cues to time annual events. Behaviors related to both seasonal timing and daily timing display individual repeatability, however it is not well understood whether a specific daily phenotype, such as earlier onset of activity, is linked to an individual also exhibiting a particular annual behavior, such as early seasonal timing in reproduction. Here we monitored the timing of daily activity across the reproductive season as well as seasonal reproductive timing of egg-laying and reproductive success in free-living female great tits (Parus major). We collected highly detailed daily accelerometer activity data from females prior to clutch initiation, as well as during laying, incubation and nestling feeding stages. We tested the hypothesis that females with an earlier daily phenotype, or a longer active day, initiate clutch initiation earlier in the season than females with a later or shorter daily phenotype. We found evidence of a positive relationship between onset of daily activity during the stages of pre-laying and laying with clutch initiation day, however there was no relationship during incubation and nestling rearing. We detected a negative relationship between pre-laying active day length and clutch initiation date. These results demonstrate a link between chronotype and seasonal timing of reproduction, but also indicate the complexity of factors that may contribute to both seasonal and daily timing of events in wild animals.
Dataset DOI: 10.5061/dryad.ffbg79d9c
Description of the data and file structure
Individual female great tits were fitted during the pre-breeding season with an activity loggers that continually tracked activity in 1 min bins until collected from the bird during the nestling rearing stage (Elderbrock et al., 2025). The data from the BitTag activity loggers was analyzed with a changepoint R analysis package (Killick & Eckley, 2014) that looked for changes in both mean and variance across an individual’s dataset (Elderbrock et al., 2025). The first switch from low to high levels of activity each morning was determined as the time of daily initiation of activity. We calculated the onset of activity by quantifying the time of activity relative to sunrise at the coordinates of the forest (Elderbrock et al., 2025; Graham et al., 2017; Schlicht & Kempenaers, 2020). Offset of activity was also calculated by determining the individual’s switch from high to low or no level of activity in the evening relative to sunset. A total length of active day in hours was calculated by subtracting the time of onset of activity from the time of offset of activity each day.
The behavioral data was divided into 5 stages for analysis:
- ActivityPrebreeding.csv: prebreeding with data relative to the first egg laid in the population
- ActivityPrebreedingInd.csv: prebreeding with data relative to an individual's first egg lay date
- ActivityLaying.csv: laying
- ActivityIncubation.csv: incubation
- ActivityChicks.csv: nestling rearing
Included in the datasheets are the following information:
- Year: year of data collection
- BirdYearID: unique bird ID
- DOY: day of year
- ChickDay: if relevant, a column displaying day of incubation, lay day, or age of chicks
- Stage: if relevant, a column displaying the stage
- SunriseTime: sunrise time on the DOY
- SunriseDec: sunrise converted
- SunriseMean: sunrise mean centered
- Day relative to first egg: the number of days relative to the individual or population
- FirstEggDOY: the day of year of the first egg laid by that individual
- DiffOnset: chronotype calculated relative sunrise
- Onset: onset time of day
- OnsetDec: onset converted
- DurationDaily: length of active day
- Day length actual: actual day length
- DayLengthActual: actual day length converted
Note: NA or blank cells are used to denote "Not Applicable" or missing data.
Code/software
We ran separate linear mixed models to ask if clutch initiation was related with chronotype quantified during different reproductive stages: pre-laying, egg-laying, incubation, and nestling rearing. Separate models were run for each reproductive stage with onset of activity and length of active day as the response variables. Date of clutch initiation and the year of sampling were included as dependent variables in each model. An additional dependent variable indicating the day within the reproductive stage was included in the models for laying, incubation, and nestling rearing (i.e. day of laying, day of incubation, and nestling age). For the models where length of active day was the response variable, the actual length of daylight (hr) was also included as a dependent variable to account for seasonal changes. In each model, individual bird ID and the day of year of behavioral data collection were included as random factors. All analyses were completed in R v.2023.12.1.