What's wrong with the yellow waist willow warblers do not reproduce

The yellow waist willow warrior does not reproduce, indicating that it has not yet reached the breeding period, or the bird's age is too young.Its breeding period is from May to July. The birds will start to match in late May. After that, the place is selected to camp. The nest is usually built on the branches, 2 meters from the ground.1-2 days after the nest, female birds began to lay eggs, with 4-5 pieces per nest.Its eggs are white jade, with red -brown spots on the surface. After 10 days of incubation, chicks will produce shells.