DOI: 10.5061/dryad.2280gb61k
title: Heavy metal pollution exposure affects egg coloration but not male provisioning effort in the pied flycatcher Ficedula hypoleuca

description: Heavy metal pollution is known to negatively affect numerous traits in
 birds, including foraging, metabolism, immunity, and reproductive success.
 In this study, our primary aim was to assess the impact of metal pollution
 exposure on the visual appearance of the pied flycatcher (Ficedula
 hypoleuca) eggs. Specifically, we focused on blue-green biliverdin-based
 coloration, a trait expected to function as a signal of female quality to
 males. In line with the sexually selected egg coloration (SSEC)
 hypothesis, which posits that males respond to more intensely colored eggs
 by increasing their provisioning effort, our second objective was to
 investigate whether metal pollution exposure affects this specific
 signaling mechanism and subsequent male behavior. Our results showed that
 although coloration did not correlate with female quality or male
 provisioning effort, egg blue-green coloration decreased in polluted areas
 compared to non-polluted control areas. Our analysis of reflectance data
 revealed that this difference was due to an increased ultraviolet
 reflectance of eggs from polluted areas, likely caused by changes in
 eggshell microstructure (e.g. porosity). We therefore propose that metal
 pollution exposure may compromise crucial color signals of bird eggs.
 Avian visual modeling indicated that eggs laid by different flycatcher
 females are generally very similar, making discrimination by males
 challenging and perhaps impossible especially in dark cavities. Overall,
 our results suggest that the SSEC hypothesis may lack adaptive relevance
 for the pied flycatcher in Northern Europe, even in environments
 influenced by anthropogenic activities.
description: ## Heavy metal pollution exposure affects egg coloration but not male
 provisioning effort in the pied flycatcher *Ficedula hypoleuca*
 [https://doi.org/10.5061/dryad.2280gb61k](https://doi.org/10.5061/dryad.2280gb61k) Mari *et al.*, Journal of Avian biology, 2024 Paper DOI: 10.1111/jav.03283 ### Description of the data and file structure #### FILE 1. Pied\_flycatcher\_egg\_coloration.txt This file contains raw coloration data for 458 flycatcher eggs, including reflectance at four image channels and cone caches obtained from photographies (refer to methods for details). This dataset was used to calculate coloration-related variables included in other datasets such as blue-green chroma and blue-green consistency (SD of chroma). Formulas are detailed in the methods. The variables are: * Label: ID number of nestbox and egg number separated by an underscore * bg_lum: luminance (brightness) * bg_lw: photon-catch values for long-wavelength-sensitive cone * bg_mw: photon-catch values for medium-wavelength-sensitive cone * bg_sw: photon-catch values for short-wavelength-sensitive cone * bg_uv: photon-catch values for ultraviolet-wavelength-sensitive cone * nest: ID number of nestbox * egg_number: arbitrary egg number attributed for image analysis * area: control or polluted * BGchroma: blue-green chroma , calculated from cone catche values (refer to methods for formula) * rank: rank of the egg in the laying sequence, if the order is known * clutch_size: number of eggs in the clutch * laying_order: known (2) or unknown (0, 1 or NA) * R_reflectance: % of reflectance of the red image channel * B_reflectance: % of reflectance of the blue image channel * G_reflectance: % of reflectance of the green image channel * UV_reflectance: % of reflectance of the UV image channel #### FILE 2. Pied\_flycatcher\_females.txt This file contains data on female body condition and egg coloration (averaged over every clutch) and was used to analyze links between egg color and female condition and generate figures 1 and 2. The variables are: * nest: ID number of nestbox * area: control or polluted * size: wing size, in mm * weight: mass, in g * SMI: standardized mass index, calculated after Peig & Green 2009 * age: female age * Neggs: number of eggs in the clutch * BGchroma: average blue-green chroma for the clutch of a given nest box, obtained from file 1 * BG.sd: average blue-green consistency for the clutch of a given nest box, obtained from file 1 * UV_reflectance: % of reflectance of the UV image channel, averaged for each female, obtained from file 1 * B_reflectance: % of reflectance of the blue image channel, averaged for each female, obtained from file 1 * G_reflectance: % of reflectance of the green image channel, averaged for each female, obtained from file 1 * R_reflectance: % of reflectance of the red image channel, averaged for each female, obtained from file 1 #### FILE 3. Pied\_flycatcher\_provisioning.txt This file contains data derived from videos on nestling provisioning (quantified as nest box visits). This dataset was used to analyze male provisioning and generate figure 3. The variables are: * nest: ID number of nestbox * area: control or polluted * n_chicks: number of nestlings in the nest at the time of recording * age_rec: age of nestlings (in days) at the time of recording * vid_duration_min: duration of recording in minutes * n_visits: total number of visits carried out by parents during the entire video * visits_hour: total number of visits carried out by parents, for one hour * M_visits: number of visits carried out by the male parent during the entire video * F_visits: number of visits carried out by the female parent the entire video * M_visits_h: number of visits carried out by the male parent, for one hour * F_visits_h: number of visits carried out by the female parent, for one hour * BGchroma: average blue-green chroma for the clutch of a given nest box, calculated from file 1 * BG.sd: average blue-green consistency for the clutch of a given nest box, calculated from file 1 #### FILE 4. Pied\_flycatcher\_chromatic\_contrasts.txt This file contains chromatic contrasts calculated between all 71 clutches included in the study. This dataset was used to analyze discriminability between clutches and generate figure 4. The variables are: * nest_combination: ID numbers of the two nestboxes being compared, separated by an underscore * mean_dS: average chromatic contrast (obtained by averaging all possible combinations of all eggs of two given clutches) * comparison.type: types of nest for which the contrast was calculated: "within-P" : polluted vs. polluted, "within-C": control vs. control, "between": control vs. polluted #### FILE 5. Blackbird\_cone\_sensitivities\_300-700.csv This file contains the cone sensitivities of the European blackbird (*Turdus merula*) that were used to compute cone catches.