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Grades K–2 · Organisms

Why does a bird smooth its feathers with its beak?

A feather can look like one smooth sheet, but it has many little branches. On a bird’s smooth outer feathers, even smaller branches have tiny hooks that catch neighboring branches.

W003 visual explanationOuter feathers have interlocking branches; A gap in the joins; Tiny hooks interlock; Enlarged branches and their small hooked side branches; Preening helps the tiny hooks line up and catch again.Outer feathers have interlocking branchesA gap in the joinsTiny hooks interlockEnlarged branches and their small hooked side branchesPreening helps the tiny hooks line up and catch again.

In the diagramOuter feathers have interlocking branchesA gap in the joinsTiny hooks interlockEnlarged branches and their small hooked side branchesPreening helps the tiny hooks line up and catch again.

An enlarged part of an outer feather shows a gap and rejoined branches. The tiny hooks are much smaller than the whole feather.

Those joins can come apart and leave a gap. When a bird runs its beak through the feather, it helps the little branches line up and catch again. This care is called preening.

A tidy feather surface helps the feather do its job in flight and in shedding water. A bird may also spread oil as it preens. The fluffy feathers close to its body are different: their loose branches help trap warm air.

About this explanation

Starting knowledge: Recognize a bird, its beak and the broad surface of a feather.

Sources

  • Cornell Lab of Ornithology — All About Feathers: How Feathers Are Built
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