People of the same sort are usually found together.
Nothing, birds shed old feathers regulary to maintain their plumage. That is all.
Did you mean Cuckoo? If so Cuckoo is the name of any of various related birds of the family Cuculidae, having grayish-brown plumage and a slender body.
Feathers. When you say "The parrot has beautiful plumage" you mean it has beautiful feathers.
to assemble
A Convention
Summer feathers. Summer plumage.
Your friends have attitudes similar to yours. It is a criticism.
It means people with similar interests or shared characteristics group together.
Assemble means to make something. It can also mean to gather a large group of people. Synonyms would be to gather, to collect, to congregate or to convene.
Only one set of feathers are grown at a time, so no feathers/plumage can be obscurred by any others. Breeding feathers are also generally considered the primary/most important, so would never be considered to obscure less important plumage. You may mean eclipse, or non-breeding plumage, which is effectively the complete opposite case as in your question.
A "wigeon" is a dabbling duck with mainly reddish-brown and gray plumage. The male has a whistling call.
i do not mean the movie birds i mean the birds