How Feathers Are Built

Light, flexible, strong, and colorful, feathers are impressive structures. Although feathers come in an amazing array of types, they are all made up of the same basic parts that have evolved small modifications to serve different functions. Downy feathers have a loosely arranged structure that helps trap air close to the bird’s warm body. The structure of other feathers features a small alteration that makes a big difference; microscopic hooks that interlock to form a wind and waterproof barrier that allows birds to fly and stay dry.

Click on a feather type at the right to learn more about feather anatomy and peek at microscopic feather structure.

array of feathers. Wing, tail, contour, semiplume, down

Click on a feather type

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The Structure of Lift

Where feathers are pennaceouspennaceouspen-AY-shusshaving an interlocking feather structure that creates a smooth surface, or vane, the many small hooks on each barbule interlock like velcro with barbules from the next barb over to form a smooth vane. This microstructure is what allows feathers to shed water and support flight.

  • Rachis

    the stiff central shaft from which the barbs branch

  • Barb

    one of the primary branches off the central rachis

  • Barbule

    one of the secondary branches off each barb

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Have you ever seen a bird smoothing feathers with its beak? This common behavior is called preening. When they preen, birds guide the barbules on their feathers into place so they fully interlock. Preening also distributes oil throughout the feathers, keeping them healthy, flexible, and waterproof. This behavior helps maintain the uniform structure that pennaceous feathers require to support flight and shed water. Playing with the slider below gives you a taste of how preening works on a microscopic level.

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example!

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The Structure of Warmth

Where feathers are plumulaceousplumulaceousploom-yoo-LAY-shusshaving a loose, non-interlocking feather structure, barbules do not have hooks and so do not interlock with nearby barbules. The barbs spread out into a fluffy mass rather than forming a flat surface. This loose microstructure traps air next to the bird’s warm body and allows some birds to stay warm through frigid winter nights of -40°F (-40°C) or colder.

  • Barb

    one of the primary branches off the central rachis

  • Barbule

    one of the secondary branches off each barb

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Have you ever worn a down vest or jacket? Inside are thousands of downy feathers. The feathers used in blankets, pillows, and coats usually come from domestic geese, but all kinds of birds grow downy feathers. Down’s loose, fluffy structure traps air next to the bird’s warm body. Because it traps air so effectively, the downy layer on ducks and other waterfowl also helps them stay buoyant. Playing with the slider below gives you a taste of how down works on a microscopic level.