At first, I didn't think anybody was home when I visited the heronry on campus Friday evening. A sudden SPLAT!! to my right, and a bit on my cheek, soon told me otherwise. Baby heron butt above.
In fact, some of them were stretching and flexing, at the very edge of their nests; I sensed their boredom, their itch to move--just like plane travellers on a cross-country flight.
When a bird runs its beak through its feathers, the behavior called preening, it is sometimes helping the sheath dislodge and fall away. Social birds, like parrots, sometimes do this for each other. And I sometimes help my cockatiel Lemon remove her sheaths with my fingers. You can see the result on my floors.