This scene is where Romeo and Juliet consummate their marriage. Juliet knows that Romeo has to leave and go to Mantua in the morning because if they see him he will be put to death. She doesn't want to believe she has to lose her husband to banishment and wants to make every moment count. Therefore she wants to believe it is the lark and not the nightingale. When the nurse calls to her to tell her her mother is coming, realith sets in and Romeo must flee.
Romeo and Juliet have had their one night together as a married couple,the only night they will ever have together. The nightingale is the bird of the night; it sings its song while the moon is out. The lark is the bird that signifies the morning sun. Juliet doesn't want to hear the lark because it means her one night of wedded happiness is over, and she doesn't know when she will see Romeo again.
The main emphasis behind the opening of these lines: Act 3 Scene 5 is on the idea that Juliet wishes that day would not come (lark) and that the night (nightingale) would last longer. Hence, Juliet tries to convince herself that the music is in fact the nightingale and not the lark. However, underneath the surface of these lines there is another symbolic meaning behind the nightingale. The nightingale is known for its song because each bird sings the exact same song. The significance of this song suggests that it was heard by some of the greatest scholars and lovers in the turn of history; one that harkens a connection between these people and immortalizes their love. Juliet may wish to revel on the idea that many lovers might have gone through the same situation that these two are in and have escaped virtually unscathed. Hence, this is the reason why the nightingale is the subject of many great poems such as John Keats “Ode to a Nightingale”.
As long as it is the nightingale signing, Juliet and Romeo can stay together just a little bit longer. A nightingale's song singals that night has fallen. When a lark sings, it is daybreak. By this point in the play, Romeo has been banished from Verona and Friar Laurence has advised him to spend the night with Juliet. This is the last time the couple can be together as man and wife.
If someone happens to see Romeo in Verona after he was banished by the Prince, Romeo will be punished for his defiance.
This quote is from Act 3.5. In the opening lines of this scence, Juliet and Romeo have spent their first wedded night together. But it is morning, the time of the lark, and Romeo must fly or face harsh punishment.
Juliet does not want the night to be over. Therefore, she feigns disbelief of the morning, insisting that the birds the lovers hear are nightingales, a bird who sings in the night (thus its name).
Here is the exchange between the two lovers (3.5.1-11):
Wilt thou be gone? it is not yet near day:
It was the nightingale, and not the lark,
That pierced the fearful hollow of thine ear;
Nightly she sings on yon pomegranate-tree:
Believe me, love, it was the nightingale.
It was the lark, the herald of the morn,
No nightingale: look, love, what envious streaks
Do lace the severing clouds in yonder east:
Night's candles are burnt out, and jocund day
Stands tiptoe on the misty mountain tops.
I must be gone and live, or stay and die.