0ISSF. Plumage varies, with non-breeding become more rusty while breeding (MAR-SEP) lose their namesake! Interesting! M/F differ, with breeding males being "uniformly black above with a blue-green to greenish gloss" and female "slate gray, darker above with a bluish green gloss". Non-breeding have the rusty and buff-brown namesake while females also have a "conspicuous pale buff line above the eye"