Smooth One's / Sb's Feathers Edit Meaning

1.

to make oneself (or somebody else) feel less irritated or offended

Lacon was no fool, and the Cousin's wrath just when everyone was trying to smooth their feathers was a thing to be avoided at any cost.

John le Carré: The Honourable SchoolboyRONET BOOKS, Hodder & Stoughton, 2000. p. 63.