Many of the field marks that we use to identify species of birds involve the color patterns created by feathers, so it is helpful to understand the basic elements that come together to form these patterns. Despite the seemingly infinite variety of bird coloration, it is limited by some simple facts about feathers. Becoming familiar with these constraints will help a lot as you develop an understanding of the birds’ appearance.
I’ve written in previous columns about how the arrangement of feathers produces and also limits the color patterns of birds (“Streaks and Spots,” December 2014 issue). In this column, I focus on the sizes of different feathers and how that influences color patterns. Generally, feather size changes from smallest and shortest at the front of the bird (around the base of the bill) to largest and longest at the back of the body, disregarding the large and specialized feathers of the wings and tail. Streaks or spots are always smaller toward the front of the bird and larger to the rear because the size of the feathers differs. This change in feather size has a profound impact on color patterns, both the intricacy and the changeability of patterns.