Molluscivorous red knots rapidly adjust to a plant diet
Data files
Mar 23, 2026 version files 682.93 KB
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DeWilde_bodymass.csv
652.96 KB
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DeWilde_Colour.csv
5.72 KB
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DeWilde_RCode.R
20.54 KB
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README.md
3.71 KB
Abstract
Dietary flexibility is key to adjusting to environmental change. In Mauritania, the seemingly obligatory molluscivorous red knots Calidris canutus canutus were observed to eat seagrass rhizomes. To study the ability of knots to live on plant material, we performed a diet-change experiment on captive individuals. Two groups of five were fed protein-rich pellets for 13 weeks, then plant-based pellets for 6 weeks, then reversed back to protein-rich pellets for 4.5 weeks. During the first days following the shift to the plant diet, body mass declined with 14% before increasing and stabilizing to lower levels. Faecal colour changed from green (i.e., gall, suggesting starvation) to brown and was produced in larger quantities when the birds ate plant pellets. These experimental data prove that knots can indeed live on a plant-based diet, the observed changes suggesting that adjustments of the digestive system, i.e., gut morphology and microbiome, take only a few days.
Dataset DOI: 10.5061/dryad.wdbrv1645
Description of the data and file structure
The data contains measurements of body mass and faecal colour of red knots to investigate the effect of a diet change on health.
Files and variables
File: DeWilde_Colour.csv
Description: Measurements of body mass and faecal colour of captive red knots following a switch to a plant diet.
Variables
- birdID: Ring code to identify individual birds
- year: Sampling year
- month: Sampling month
- day: Sampling day
- food: Indicating the plant diet received during the measurements
- cage: Aviary room identifier
- mass: Body mass (gram)
- massdiff: Difference in mass since last measurement (gram)
- R: Red colour measured in stool sample
- G: Green colour measured in stool sample
- B: Blue colour measured in stool sample
- HEX: HEX-code generated from R, G and B
File: DeWilde_bodymass.csv
Description: Body mass measurements of red knots held in aviaries during a diet-change experiment, performed from October 2023 until March 2024. Historical body mass measurements from 2017 until 2021 of individuals held under similar environmental and seasonal conditions.
Variables
- date: Date of sampling
- bird_ID: Ring code to identify individual birds
- mass: Body mass (gram)
- weekinyear: The number of the week of the year during which the sample was taken according to ISO
- weekinexp: The number of weeks since the start of the experiment
- winter: The year in which the winter season started
- group: Group of birds (historical or experimental)
- diet_phase: A distinctive period of time indicated by the type of diet received during a particular period in the experiment.
- control_historical: body mass measurements of individuals in captivity in the years 2017-2021, while on the control diet
- control_pre: body mass measurements of individuals in the year 2023, while receiving the control diet in the period before the experimental diet
- vegetarian: body mass measurements of individuals in the year 2023, while receiving the experimental (vegetarian) diet
- control_post: body mass measurements of individuals in the year 2023, while receiving the control diet in the period after the experimental diet
- diet: Diet during the measurements
- Trouvit: high protein control diet, fish-based pellets
- vegetarian: experimental diet, plant-based pellets
- year: Sampling year
- month: Sampling month
- day: Sampling day
- dayinyear: The day in the year during which the sample was taken according to ISO
- days_since_experiment: The number of days since the start of the experiment in 2023, counting from the day in the year
- days_since_veg_stop: The number of days since last receiving the plant diet, counting from the day in the year. Not applicable (NA) for measurements before this date
- days_since_veg_start: The number of days since first receiving the plant diet, counting from the day in the year. Not applicable (NA) for measurements before and after receiving the plant diet
File: DeWilde_RCode.R
Description: R code used to perform the statistics of the manuscript using R version 4.4.1. Inputfile: DeWilde_bodymass.csv. Packages: dplyr (1.1.4), mgcv (1.9-1), ggplot2 (3.5.2), lme4 (1.1-37), tidygam (1.0.0), ggbeeswarm (0.7.2), lubridate (1.9.4), lmerTest (3.1-3), emmeans (1.11.1), broom.mixed (0.2.9.6), car (3.1-3), Metrics (0.1.4), nlme (3.1-164) and purrr (1.2.0)
Access information
Other publicly accessible locations of the data:
- n/a
Data was derived from the following sources:
- n/a