Songs of one species mean nothing to birds of another species. Robins, cardinals, catbirds, and yellowthroats might all nest in the same garden without interfering with each other. Robin's songs are only meant to keep other male robins away. The songs of the male robin mean nothing to the male cardinal, catbird or yellowthroat. Unless another bird is a predator, a species of bird simply ignores all other species of birds.
Young birds know already how to sing.
The young birds' songs have the same basic patterns and sequences as in the adults' songs. What the young bird's song lacks is the more difficult, more musical part of the song. By listening to the male parent singing during the summer months, the young bird gradually adds notes to the basic song. It is also possible to hear the young birds practising in early spring. These birds are not yet ready for territorial singing but practice a version of the territorial song that is quieter and lower in tone.