Chirpiness is the happy, lively quality itself — the being-chirpy. If a person has chirpiness, they seem bright, ready to talk in a light way, and full of small energy, like a bird that cannot sit still because the morning is good. We use it for people more than for things. It is everyday English and a little cute; you might smile when you say it. It is not the same as being loud, and it is not the deep happiness that comes after big news. It is the everyday sparkle in someone's voice or manner. You hear it more in British English. Though actually, people do not use this noun as often as chirpy: "She's so chirpy this morning" is the sentence you will meet most. Both are real.