How many months of the thrush bird changed hair for a few months

The thrush bird changed hair in July and August.Due to the differences in temperatures in various regions, the hair change period of thrush birds will also be accompanied by the delay or advance in the temperature.However, whether it is delayed or early, it will generally not exceed one month.If there is no hair change, it may be that birds are sick.The normal order of changing hair is from top to bottom, from beginning to the tail. If it starts from the tail, it means that the change of hair is not normal this time.