What is going on without breeding?

The yellow bird does not reproduce, indicating that it has not yet reached the reproduction period, or usually insufficient nutrition, resulting in a late development.This bird usually starts to breed in June. Before breeding, the nest is required. The birds will built the nest on the tree, and the fiber, animal hair, and so on.The nest is generally completed by the male and female birds. After that, the female birds start to lay their eggs. Each nest can produce 4-6 pieces. After 14 days of incubation, the female will be the shell.