While not a terribly common occurrence, as an active birder, you might come across a bird at some point that just doesn’t quite fit your handy field guide’s plumage colour description. These birds look very familiar to us, but for one reason or another, their true colours are not showing through.
Some examples of these oddities are cardinals that are white or yellow in colouring, rather than their striking red plumage, or house finches that also seem to be coloured an orange or yellow colouring, likely due in part to one of the below oddities that affect feather and plumage colouring in the bird world.
Xanthochroism or Xanthism
This disorder usually is responsible for the dominant yellow colouring in birds and is usually caused solely by genetics. This abnormality removed dark pigments from the bird’s plumage, allowing the yellow to become more dominant. The unfortunate part of this condition is that it is often passed down as affected birds have difficulty attracting willing mates with the proper plumage colouring.
Related to Albinism (below), this condition renders feathers and plumage to be a dull colouring, but not quite an exact white colour. This disorder dilutes natural pigmentation, but in most cases, field markings like bars, masks and wing bars remain detectable.
Derived from the word Albino, you guessed it, these birds are completely white in colour. This condition is genetic and interferes with the production of melanin and often renders the birds to have no pigmentation whatsoever.
Quite the opposite of the above, this condition is witnessed in birds having a genetic mutation which causes excessive dark pigmentation. These birds will appear very dark in colouring and can be quite challenging to decipher, depending on how extreme their condition is.