Meeting Abstract

S2.3-2  Saturday, Jan. 4 14:00  The mechanisms of condition-dependent variation in melanin-based plumage color. D’ALBA, L.*; SPENCER, K.A.; VAN HEMERT, C.; HEIDINGER, B.J.; GILL, L.; EVANS, N.P.; MONAGHAN, P.; HANDEL, C.M.; SHAWKEY, M.D.; University of Akron; University of St. Andrews; USGS Alaska Science Center; University of Glasgow; Max Planck Institute for Ornithology; University of Glasgow; University of Glasgow; USGS Alaska Science Center; University of Akron liliana@uakron.edu

Carotenoid-based plumage color is clearly condition-dependent, fulfilling a key prediction of honest advertisement models of sexual selection, but whether the same holds true in melanin-based colors is still unclear. Here we first provide direct experimental evidence of condition-dependence in a eumelanic (black bib of black-capped chickadees, Poecile atricapillus) and pheomelanic (cheek feathers of zebra finches, Taeniopygia guttata) ornament. However, to provide a direct link between condition and trait expression, it is necessary to understand the proximate mechanisms underlying variation. Therefore, we use transmission and scanning electron microscopy and light microscopy to investigate how feather micro and nano-structure affect reflected color and is in turn affected by stress (either from disease or food unpredictability). We show that reflected color is a product both of melanin density and the larger-scale spacing and density of feather barbs and barbules. Thus, stress affects both pigment deposition and feather structure, leading to variation that honestly reflects underlying condition.