I know that this part is performed by the flute. What is the name of the symphony?
I would say it's "Morning Mood" from Edvard Grieg's Peer Gynt Suite No. 1.
Peer Gynt started life as incidental music to the play of the same name by Henrik Ibsen; it included vocal as well as instrumental parts. Grieg later made two purely orchestral suites from it, "Morning Mood" (or, popularly, just "Morning") being the opening movement of the first suite.