What happens to sparrows that don't learn their song during the critical period?

They must wait and learn the song one month later.

The sparrows have lost their chance to ever fully learn their song,

They must rely on adult sparrows to teach them the song for several extra months,

All statements are true.

The Sparrows have lost their chance to ever fully learn their song

Explanation:

when the sparrows don't learn their song during the critical period they can never learn it again fully. sparrows are lovely birds that have some very important symbols in the society like they represent diligence, hard work, caution and courage. they also represent joy and protection.

Sparrows chirp with their beautiful voices which is seen or heard as singing and every sparrow learns how to do this during the critical period and if the sparrow misses out on that critical period it will never really  learn it fully again.