The male Allen's has a green back and forehead, with rust-colored rufous flanks, rump, and tail. The male's throat is also an iridescent orange-red. The female and immature Allen's Hummingbirds are similarly colored, but lack the iridescent throat patch, instead having a series of speckles on their throat.
Fun Fact The male is also highly aggressive and territorial. A male will chase any other males from its territory, and they have even been known to attack predatory birds several times larger than themselves such as kestrels and hawks.