Just feathers pinned to it. Was common to have overly decorated hats if you could afford it in ways we wouldn't consider fashionable today (Mrs. True's hat looks like a modern flower cake also lol). This tradition is not dead, for some modern examples check out the royal ascot races, kind of a fun/funny tradition.
Some hats even had full (dead) birds on them. It was a short lived trend as many people objected to it.
I've probably played too much Dark Souls for this to be my first thought, but:
Mrs True knows how to shut him up. They are a perfect couple.