[Various bird calls] [Three common tern chicks are huddled together in a shallow nest among rocks. They move around, but stay close together.] [Explore Macaulaylibrary.org]

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In order to stay warm, many young birds have a special set of fluffy feathers, known as natal down, that function as a coat. These feathers insulate the bird while their parents are out foraging and will eventually be lost and replaced by their adult contour feathers with a layer of down underneath them.

This video accompanies Chapter 4, Feathers and Plumages, Handbook of Bird Biology, 3rd Edition from the Cornell Lab of Ornithology and Wiley Publishing.

Recorded by Benjamin M Clock, Macaulay Library