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How the sizes of birds’ various feathers influence color patterns

bird feathers
Two views of a Song Sparrow: The illustration at left shows the full color pattern with a flank feather and a throat feather on the side. At right is the same bird with its feather edges outlined to show the change in size of feathers from the head to the body. Art by David Sibley

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.

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David Sibley

David Sibley

David Sibley writes the column “ID Toolkit” in every issue of BirdWatching. He published the Sibley Guide to Birds in 2000, the Sibley Guide to Bird Life and Behavior in 2001, and Sibley’s Birding Basics in 2002. He is also the author of the Sibley Guide to Trees (2009), the Sibley Guide to Birds-Second Edition (2014), guides to birds of eastern and western North America (2016), and What It’s Like to Be a Bird (2020). He is the recipient of the American Birding Association’s Roger Tory Peterson Award for lifetime achievement in promoting the cause of birding and a recognition award from the National Wildlife Refuge System for his support of bird conservation.

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