Female mallard (Anas platyrhynchos) resting on a trunk on the Prosna river.
In birds, it is common for females to have dull-colored feathers (brownish, greyish etc.) so it is harder for predators to spot them. In contrast, many male birds have fantastic, colorful plumage to impress the ladies (and some predators, too…).
See the blue part with white edges standing out from the brown feathers? These are so-called ‘speculum feathers’ (in Polish lusterko = ‘mirror’).