The vast majority of waterbirds change their plumage in their breeding season. Male and female birds also have different plumages. Thus a single species may have four distinct adult plumages, not to mention the changing appearance of their young.
絕大多數水鳥在繁殖期會換羽，加上雌雄羽色不同，光一種鳥就有 4 種不同羽色，如果再加上幼鳥則變化更多。