Comparison of Feather Pigments in Red-Winged Blackbirds (Agelaius phoenicus) Between Historical and Modern Samples

Coloration is vital to birds; it is involved in mating, territorial display, communication, camouflage, and predation. Birds rely on their environment for the raw materials necessary to make most colors present in their feathers. As a result, habitat quality can have lifetime fitness consequences through the color pathway. Widescale habitat change has affected the quality of habitats accessible to birds worldwide. Consequently, the availability of pigment-containing resources within many altered habitats has shifted, leading to modification in the coloration of some birds’ feathers. I hypothesized that the red pigmentation in the feather shoulders, or epaulets, of red-winged blackbirds (Agelaius phoenicus) may have changed in Connecticut’s population over time. To test this hypothesis, I compared the carotenoid pigments of epaulet feathers from red-winged blackbird specimens collected around 1970 to those of feathers from birds captured in 2016. Historical feathers were sampled from museum specimens and were evaluated relative to new feathers taken from live birds. Feathers were visually scored for pigmentation intensity, and then carotenoids were extracted and identified using high performance liquid chromatography and spectrophotometry. The pigment profiles of the museum specimens show that the historical birds were able to retrieve and produce the expected pigments in their epaulets whereas the live birds lacked one of the two major carotenoids that constitute epaulet coloration. The habitat of the modern birds may not have had the adequate resources for the individuals to build all of the expected carotenoids in their epaulets. This observation could indicate the effect of habitat quality on carotenoid pigmentation in birds from 1970 to present day. To better understand this effect, analysis of temporal habitat change must be paired with a robust study of pigmentation change over time.