Ectoparasite Abundance and Individual Color Variation in Three Cardueline Finch Species

Abstract

Elaborate and/or colorful bird plumages have often been hypothesized to evolve via sexual selection for increased ornamentation. Differences in coloration among individuals can be influenced by a number of variables, including diet, hormones, and disease resistance. Specifically, Hamilton and Zuk 22 (1892) hypothesized a link between an individual’s parasite resistance and more colorful plumage signals, as a mechanism for individuals to advertise their ‘quality’. While much data has accumulated documenting the nutritional and hormonal regulation of various types of plumage coloration, relatively little data exists reporting the effects of parasite load on individual plumage colors (i.e. melanin and carotenoid pigmented feathers). We collected ectoparasites and plumage color data from 24 purple finches (Carpodacus purpureus), 11 pine siskins (Carduelis pinus), and 21 American goldfinches (Carduelis tristis). We found substantial individual variation in both total parasite load and quantified measures of feather coloration, and we report on the association between these variables among individuals within each species.