A comparison of spectrophotometry and color charts for evaluating total plasma carotenoids in wild birds

The study of the role of carotenoids on the physiology and evolutionary eco logy of birds demands methods for their quantification in the bloodstream W e compared color-chart scores of plasma hue with the actual concentration o f plasma carotenoids obtained by spectrophotometry in 356 wild birds from 2 6 species. Repeatability of chart scores between three independent observer s was high. However, color scores did not correlate with the spectrophotome tric results in interspecific analyses. Within species (n = 3), one showed no relationship and two showed weak but significant positive correlations. Hemoglobin, and probably other substances, may mask the color of carotenoid s, making the accurate use of color charts difficult. Spectrophotometry sho uld be the method of choice as it permits precise quantifications of total plasma carotenoids and objective comparisons among studies.