How the Sizes of Different Bird Feathers Influence Color Patterns

Many of the land marks we use to identify bird species involve the color patterns created by feathers, so it is useful to understand the basic elements that come together to form these patterns. Despite the seemingly endless variety of bird coloration, it is limited by a few simple facts about feathers. Familiarizing yourself with these constraints will go a long way in developing an understanding of bird appearance.

I’ve written in previous columns about how feather arrangement produces and also limits color patterns in birds (“Streaks and Spots”, December 2014 issue). In this column, I focus on the size of different feathers and how that influences color patterns. Typically, feather size ranges from the smallest and shortest at the front of the bird (around the base of the beak) to the largest and longest at the back of the body, disregarding the large specialized wing and tail feathers. The streaks or spots are always smaller towards the front of the bird and larger towards the back because the size of the feathers differs. This change in feather size has a profound impact on the color patterns, both the complexity and the variability of the patterns.

Tiny feathers on the head can each be colored differently to form a highly detailed tapestry of colors. Each feather can be a solid color, but a pattern is created by arranging many tiny feathers with contrasting colors. And because these feathers are short and stiff, they don’t flex or move, and the pattern always stays the same.

Much larger and longer feathers on the body provide a coarser “template” on which to apply a pattern. Each individual feather may show a single black streak or spot, but relatively few feathers are involved. And because these feathers are long and flexible, their tips can move across other feathers and the pattern of the streaks shifts. The striations on the flanks can be arranged in three lines, two lines, no lines, a criss-cross pattern, etc., all on the same individual bird over a short period of time.

This is one of the main reasons why head models are so much more useful for identification. When looking at head models, the details really matter. The exact shape of the pale markings around the eye, the shape of a pale eyebrow, the color and pattern of the crown stripes, etc., are all reliable and consistent, never changing as the bird moves.

Think about feather size when birdwatching this season and see what you can learn about how feather size and color pattern are related.

This article first appeared in the November/December 2021 issue of BirdWatching magazine.