The color of greater flamingo feathers fades when no cosmetics are applied.

Sophie Labaude,Antonio Pérez‐Gálvez,Araceli Garrido,Miguel A. Rendón,Anne‐Sophie Deville,Juan A. Amat,Maria Cecilia Chiale,Juan Garrido‐Fernández,Manuel Rendón‐Martos,Arnaud Béchet

doi:10.1002/ece3.8041

Abstract

Greater flamingos use cosmetic coloration by spreading uropygial secretions pigmented with carotenoids over their feathers, which makes the plumage redder. Because flamingos inhabit open environments that receive direct solar radiation during daytime, and carotenoids bleach when exposed to solar radiation, we expected that the plumage color would fade if there is no maintenance for cosmetic purposes. Here, we show that the concentrations of pigments inside feathers and on the surface of feathers were correlated, as well as that there was a correlation between the concentrations of pigments in the uropygial secretions and on the surface of feathers. There was fading in color (becoming less red) in feathers that received direct solar radiation when there was no plumage maintenance, but not so in others maintained in darkness. When we controlled for the initial color of feathers, the feathers of those individuals with higher concentration of pigments on the feather surfaces were those that lost less coloration after experimental exposure of feathers to sunny conditions. These results indicate that exposure to sunlight is correlated with the fading of feather color, which suggests that individuals need to regularly apply makeup to be more colorful. These results also reinforce the view that these birds use cosmetic coloration as a signal amplifier of plumage color. This may be important in species using highly variable habitats, such as wetlands, since the conditions experienced when molting may differ from those when the signal should be functional, usually months after molting.

Highlights

The color of feathers is due to pigmentation or structural coloration (Gill, 1990)
The adult greater flamingos use much less frequently the behavior employed to spread the uropygial secretions over their plumage with cosmetic purposes than during the months preceding chick hatching, which together with a decrease in the concentration of carotenoids in the uropygial secretions results in a fading of plumage coloration in about a month (Amat et al, 2011, 2018)
We demonstrate that the neck plumage coloration would fade during such a long period when there is no possibility of plumage maintenance

Summary

| INTRODUCTION

The color of feathers is due to pigmentation or structural coloration (Gill, 1990). Because feathers are inert tissue and pigments are deposited into feathers during molt (Gill, 1990), it has for long been assumed that feather coloration was a relatively static trait. There are an increasing number of evidences showing that feather coloration may change between molting periods, even during short-term ones This may be due to accidental staining with organic or inorganic substances (Ficken & Ficken, 1962; Kennard, 1918; Shawkey et al, 2011; Surmacki, 2011; Surmacki & Nowakowski, 2007), abrasion (Fig uerola & Senar, 2004; Surmacki et al, 2011; Veiga, 1996; Willoughby et al, 2002), saprophytic fungal growth (Clubb & Herron, 1998), denaturation of pigments (Blanco et al, 2005), or to the deliberate application of some substances over the feathers by the birds themselves (i.e., cosmetic coloration; Delhey et al, 2007; Montgomerie, 2006; Negro et al, 1999; van Overheld et al, 2017; Pérez-Rodríguez et al, 2011). We predicted that the degree of plumage fading when there is no plumage maintenance should be related to the quantity of pigments deposited as makeup over feathers’ surfaces

| MATERIALS AND METHODS

Findings

| DISCUSSION