DOI: 10.5061/dryad.f4qrfj6x7
title: Experimentally impaired female condition does not affect biliverdin-based egg colour

description: It has been proposed that blue-green egg coloration is a
 condition-dependent female sexual trait that may modify paternal care in a
 post-mating sexual selection scenario. This pattern may arise because the
 pigment responsible for eggshell colouration (biliverdin) may be a costly
 and limited resource, whose availability is linked to female health state.
 Thus, it can be predicted that females whose condition is compromised
 should be constrained in their capacity to deposit biliverdin in the
 eggshell, thus producing paler clutches. To test this hypothesis, we
 performed a handicapping experiment by clipping some feathers of female
 spotless starlings before egg laying and measuring the colour of their
 clutches. We expected the handicapping treatment to increase flying costs,
 impairing female overall condition and resulting in paler clutches. Our
 experiment was successful in lowering the weight gain of handicapped with
 respect to control females. However, in contrast to our expectations, we
 found no effect of the treatment on eggshell colouration. Eggshell colour
 varied along the laying order, with initial eggs of the laying sequence
 being relatively paler than the rest of the clutch, but this pattern was
 not different between experimental groups. Despite a very similar
 methodology, our results differ from a previous study and offers no
 support to the post mating sexual selected hypothesis, questioning the
 general applicability of the sexual selection role of eggshell coloration.
description: Dataset 1: this is the dataset used for the eggshell coloration
 analysis. The dataset presents 145 columns and 197
 lines. Each line represents the data relative to a single starlin egg
 considered for the analysis. Column 1 is the original
 ID of the egg in the field noterbook.<br>Column 2 is the individual
 code for each breeding attempt (i.d. every time a first egg is found in a
 nest).<br>Column 3 is the nest in which each egg has been
 found.<br>Col. 4 is the tratment to which the female laying the eggs
 has been subjected: H, handicap; C, control.<br>Col. 5 contains the
 date of measurement of the eggs.<br>Col. 6 contains the date of
 laying of each egg (date of April 2020).<br>Col. 7 the clutch size
 of each breeding event.<br>Cols. 8-10 the lenght (mm), widht (mm)
 and the calculated volume (mm<sup>3</sup>) of each egg. Please
 refer to the main text for more information about egg size
 calculation.<br>Cols. 11-15 contain the informations about the
 laying female (IDs and measurements). <br>Cols. 16 - 135 contain the
 repeated measurements of eggshell coloration as stored in the
 spectrophotometer and the relative values of brightness, BGC, hue and
 chroma. The x and y are used to distinguish the first from the second
 spectra values.<br>Cols. 136-139 contain the values of the mean
 value of brightness, hue, chroma and blue-green chroma for the repeated
 measures (x and y).<br>Cols. 140-142 contain the main, the standard
 deviation and the maximum values of BGC for each nest.<br>Cols.
 143-145 contain the main, the standard deviation and the maximum values of
 BGC x100. Dataset 2: this dataset contains the data of
 the females recorded before and after the laying. Col.
 1 and 2 contain the ID of the female (ring number and chip code,
 respectively)<br>Col.3 the tratment to which the female laying the
 eggs has been subjected: H, handicap; C, control.<br>Col. 4 the nest
 in which the eggs have been laid.<br>Cols. 5 and 6 contain the dates
 in which the female has been captured (before and after laying the eggs,
 respectively).<br>Cols. 7 and 8 contain the day counts of the
 corrispective date, starting the day of the laying (April
 11<sup>th</sup>).<br>Col. 9 and 10 contain the initials
 of the observer of the first and second capture.<br>Col. 11 contains
 the coded age of the oldest nestling: P5, chick of 5 days; P6, chick of 6
 days...<br>Cols. 12 and 13 contain the weights recorded in the first
 and in the second capture (pre and post laying,
 respectively).<br>Cols. 14 and 15 contain the wing (mm) and the
 tarsus (mm) measurements of the females, recorded in the first
 capture.