Two distinct processes are involved in molting. The first step is when the old, worn feather is dropped, or shed. The second is when a new feather grows in its place. When each feather has been shed and replaced, then the molt can be said to be complete. This, however, is an abstraction that often does not happen: incomplete, overlapping, and arrested molts are quite common.
I feel the word “arrested” in the sentence above is hard for me to understand. Does it mean “delayed” or something else?
Could you explain it?
Good question! Delayed would indicate that there is an interruption, and the process resumes later on. Arrested means stopped; there is no indication that the process will later resume.