DOI: 10.5061/dryad.d7wm37q8s
title: Quantitative genetics of eggshell colouration

description: Exploring the evolutionary architecture of female sexual traits and their
 potential evolvability is important to understand their possible role as
 post-mating sexual signals. Egg colouration has been proposed to be one of
 these post-mating sexual signals, honestly advertising female quality in
 birds, especially in blue-green laying species. In this study, we used an
 animal model in a Bayesian framework to estimate the evolvability of
 multiple descriptors of blue-green egg colouration and egg size in a wild
 long-term monitored population of spotless starlings (Sturnus unicolor).
 Our results show low to moderate heritability (h2 = 0.31 – 0.44) for three
 egg colour descriptors (blue-green chroma, chroma and lightness) and egg
 size. Using the coefficient of additive genetic variance (CVA) and the
 evolvability (IA) as proxies of evolutionary potential of all components
 of this trait, we found low values of CVA for all these variables,
 suggesting a small evolutionary potential of these phenotypic traits,
 contrasting to previous results reported in another blue-green egg laying
 species. Our results indicate a modest raw genetic material of this trait
 on which sexual selection can act upon and, therefore, a small probability
 for these traits to respond easily to selection.
description: We monitored the breeding of a population of spotless starlings
 (<em>Sturnus unicolor</em>) from 2012 to 2019 nesting in 250
 nest boxes in an open woodland in Soto del Real, central Spain. At the
 beginning of every season, from early March until about a week before the
 first eggs were found, we captured the pairs roosting in the nests before
 sunrise.  Bird identities of previously captured
 individuals were confirmed by both the ring number and the unique code of
 a passive integrative transponder tag (PIT-tags:  Trovan Ltd., Douglas,
 UK). Previously unmarked individuals were ringed and PIT-tagged by
 inserting the transponder under the skin of the upper third of the back.
 Later in the season, fledglings were similarly marked to ease their future
 identification as recruits. Once pairs were established
 and the eggs laid, mothers were identified at night during incubation
 through a medium-distance PIT-tag reader (GR-250, Trovan Ltd., Douglas,
 UK) allowing us to unambiguously assign each clutch to a female.
description: # Quantitative genetics of eggshell colouration
 [https://doi.org/10.5061/dryad.d7wm37q8s](https://doi.org/10.5061/dryad.d7wm37q8s) This dataset represents an extensive study on the quantitative genetics of eggshell coloration in Spotless starling (*Sturnus unicolor*). The study was conducted over 8 years and involved the detailed recording of various attributes related to eggs, nests, and parentage among bird individuals. The primary aim was to analyse the genetic architecture of chromatic and achromatic colour components (blue-green chroma, chroma and lightness) and size (volume) of starling eggs. The text file contains the pedigree (non-pruned) used in the animal model. ## Description of the data and file structure The dataset is contained in a single CSV file named `Quantitative genetics egg coloration_repository.csv`. Each row in the file represents an individual egg, capturing a range of variables related to its physical characteristics, parentage, and other relevant factors. ### File Structure * **CSV File Name:** Quantitative genetics egg coloration_repository.csv * **Number of Entries:** 11,002 rows * **Columns:** The file contains a single column with multiple attributes separated by semicolons (`;`). ### Columns and Variables 1. **EVENT**: Event identifier 2. **Year**: Year of data collection 3. **Nest**: Nest identifier 4. **Clutch**: Clutch number 5. **Lay.order**: Order of laying within the clutch 6. **ID.Egg**: Egg identifier 7. **animal**: Laying female identifier 8. **dam**: Mother (dam) of the female identifier 9. **sire**: Father (sire) of the female identifier 10. **Pair**: Pair identifier 11. **Age**: Age of the mother at the time of laying 12. **Age.cat**: Categorical age of the mother 13. **Weight**: Weight of the egg (in grams) 14. **Wing**: Wing length of the mother (in mm) 15. **Tarsus**: Tarsus length of the mother (in mm) 16. **Bill**: Bill length of the mother (in mm) 17. **Capture.date**: Date of capturing the egg (dd/mm/yyyy) 18. **OBS**: Observer initials 19. **Length**: Length of the egg (in mm) 20. **Width**: Width of the egg (in mm) 21. **Volume**: Volume of the egg (calculated in cubic mm) 22. **Brightness**: Brightness of the egg coloration 23. **Chroma**: Chroma (color intensity) of the egg coloration 24. **BGC**: Blue-green chroma color of the egg ### Definitions and Units * **Missing Data Codes**: `NA` denotes missing data. * **Units**: * **Weight**: grams * **Wing, Tarsus, Bill, Length, Width**: millimeters * **Volume**: cubic millimeters * **Brightness, Chroma**: dimensionless units representing color metrics