What happens to the colorful outer sheath of a puffin's bill outside the breeding season?

Answer

The outer sheath is shed, making the bill smaller and duller.

The dramatic, colorful bill is a seasonal feature; the outer sheath is shed when the bird is wintering or outside the breeding period, resulting in a smaller, duller bill.

What happens to the colorful outer sheath of a puffin's bill outside the breeding season?
birdanimalclassificationPuffin