You who live in the mountains or plantations will certainly hear the birds chirp in the morning. Scientists call the event as a dawn chorus phenomenon. Birds usually start activities at 4:00 am and end in a few hours later to find food.
Although birds can sing all day long, but the frequency of chirp in the morning will sound louder and often. Most of the chirping you hear comes from a male. Usually it is done to attract the attention of the opposite sex and also become a harbinger of territory or territoriality from other males.