We talk about something being as light as a feather. For the average bird, what percent of its weight is due to its feathers?
For most birds, their feathers make up 15% to 20% of their total weight. On the other hand, their skeletons are so light that they only make up 5% to 10% of their weight. Those figures are accurate for most birds, but not for flightless birds such as ostriches or penguins. They have much heavier bones.
By the way, this bird is a Purple Gallinule that I photographed in the Everglades.