Natural soiling has a small effect on structurally-based plumage coloration

Abstract

Plumage coloration is an important trait used by birds in mate choice decisions and is often an indicator of social status. The two main types of color-producing mechanisms in feathers are pigment deposition (pigmentary coloration) or the coherent scattering of light reflected from keratin microstructure (structural coloration). External factors acting on the feather surface are also hypothesized to affect structural coloration. Because preening is an energy and time demanding behavior, color variation caused by soiling deposition is generally assumed to strengthen the condition signaling function of plumage coloration. To date, studies using artificial soiling have confirmed those hypotheses. However, information about how natural soiling affects plumage color are still scarce. In this paper, I investigated the effect of natural soiling on structurally-based feather color of blue tits Cyanistes caeruleus. As a method, I applied mechanical cleaning that functionally mimicked natural preening. Removal of soiling caused a decrease of ultraviolet (UV) chroma in males and decrease in brightness in females. According to visual contrast modeling, only changes in brightness should be perceived by birds. Further, more efficient chemical cleaning resulted in a significant increase in brightness in both sexes, presumably due to preen wax removal. These results suggest that the impact of natural feather soiling is not likely to modify structural coloration signaling. One possible explanation is that, under natural conditions, the amount of soil accumulating on feathers is too small to affect coloration.

When to measure plumage reflectance: a lesson from Collared FlycatchersFicedula albicollis

“…), changes in the thickness and composition of the preen gland wax (Pérez‐Rodríguez et al . , Surmacki ) and, for carotenoid‐based traits, also pigment degradation (McGraw & Hill , Surmacki , Higginson et al . ).…”

Sex-associated differences in trace metals concentrations in and on the plumage of a common urban bird species

“…Grooming could then also efficiently eliminate metals, among other particles, from the surface of the plumage, and explain our observations. Urban pollution could also alter plumage quality by altering visual characteristics (such as in reflectance in UV range and yellow chroma Griggio et al 2011;Pérez-Rodríguez et al 2011;Surmacki 2011) and select for increased plumage care among males. Interestingly, we found differences between metals: contrary to what we found for the three other metals, external depositions in zinc were similar between males and females.…”

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

“…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;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).…”

“…But 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 ). Both male and female greater flamingos Phoenicopterus roseus apply over their plumage, as makeup, uropygial secretions pigmented with carotenoids that make their feathers redder (Amat et al., 2011 , 2018 ).…”