Why do birds plummage differ

[revpat55]

Does anyone know why there is no difference between the plummage of male & female birds in certain species like crows, magpies, swans & buzzards, yet males of other species are much more flamboyant than the females e.g. finches, sparrows & ducks.

[boxtops]

Swans and crows and magpies mate for life so once they've found their female, they don't need to flounce about showing off. However I think some ducks do too, so that blows my argument out of the water if so. Really flashy birds like peacocks need to attract a new female each year which is why they go to so much effort.

[revpat55]

My husband thought the same sort of thing - very possible & thank you

[wildwood]

As a rule (but not always) with birds that are sexually dimorphic [the male is a markedly different colour from the female] the hen does all the incubation, therefore are cryptically coloured to hide when sitting on the eggs.

With the open nest builders (as opposed to birds that nest in tree holes and caverns) the cock sometimes covers the eggs to hide them from predators, but they do not develop the blood vessel gorged brood patch, so can not keep the eggs warm.

There are other more complicated reasons and some just don't make sense to us but they must be beneficial to the birds or 90% of them wouldn't have been around for 10+ million years in their present form.