Up with the lark means awake very early in the morning. She is up with the lark every day.
The lark sings before dawn, which is what makes it the measure. It is admiring and slightly old-fashioned, and it belongs to country speech.
1phraseup with the larkAwake very early in the morning.
“He was up with the lark and out before anybody stirred.”
up with the lark is a phrase.
Practised in Idioms