I want to know the answer to the following question:
What is regularly moulted?
All the background I'm provided with is that "Plumage is regularly moulted; the standard plumage of a bird that has moulted after breeding is known as the "non-breeding" plumage, or—in the Humphrey-Parkes terminology—"basic" plumage; breeding plumages or variations of the basic plumage are known under the Humphrey-Parkes system as "alternate" plumages.". Is that enough to answer the question?
Answer: yes