Nobody here but us dandelions - American goldfinch

Does the bright yellow colour of goldfinch males make them easier prey for predators?

The phrase "Sticking out like a sore thumb" could be applied to male goldfinches.  Not only are they a bright dandelion yellow, but they have dark, black contrasting feathers that make them stand out even more.  What evolutionary pressures would shape such a creature?

Birds of prey and predatory mammals such as cats have colour vision and sharp eyes that pick up not only the colour of the male goldfinch birds but their strong contrast too.  Female goldfinches (see below) have more subdued yellows, less black, and do not have a stark black cap.  Of the two birds, the male is more likely to be seen and hunted.  This gives the female a better chance at incubating the eggs and rearing the young.

Male (left) and female (right) American goldfinches.

The bright yellow of the male also acts as a signal to females of his fitness for breeding.  The bright yellow colour comes from pigments called carotenoids.  These chemicals are found in seeds, fruits, flowers, and greens.  The birds' colours cannot be made without the proper precursors.  The carotenoids allow the development of bright feathers which is an attractive quality in a mate.  It essentially means that the bird is successful at foraging for food.

The fall moult produces males that look remarkably similar to the females.  Since breeding is off the table, the subdued colours reduce predation and increase the chance for the male to breed in the coming spring.  The females would not be interested in a dully clad male, and so the spring moult produces the familiar brilliant feathering that gives the bird its name.

Thanks for reading.

Eric Svendsen     www.ericspix.com