Correlation between Color, Body Condition, and Diet in the Lesser Goldfinch

Abstract

Bright plumage is thought to be a true indicator of body condition because consuming high quality forage forms brighter plumage. Plumage coloration is an important secondary sexual characteristic. The relationship between winter plumage coloration and fitness is not well understood in the Lesser Goldfinch (Spinus psaltria). I collected body measurements, pictures of plumage, feathers, and blood of goldfinches to assess the relationship between them. I assessed body condition by correcting mass with body size to get an understanding of how color reflects the body condition of the goldfinch. Plumage coloration was not correlated with body condition; however, the “L” (brightness of the breast plumage) value had a negative correlation with values of carbon (?13C). The stable isotope values provided dietary information for individual goldfinch. Further, results showed temporal and spatial differences in diet between birds collected from rural and urban sites. Understanding the correlation between color, body condition, and diet can provide insight into the evolutionary context of the three traits.