What's wrong with the ten sisters and birds do not reproduce

Ten sisters do not reproduce, it is likely that they feel that environmental discomforts, or lack of nutrition, or they may be the consistency of the two birds.Let this bird reproduction requires materials to make it built, and can prepare some dry grass, feathers, etc.It can produce 5-6 nests a year, with 3-5 pieces in the first nest, and the second nest will increase to about 8.It takes 12 days to hatch, and the feathers can grow after 21 days of the shell.