Male ostriches weigh up to 155 kg. and are larger than females. The feathers of adult males are mostly black, with some white at the wings and tail. Females and young males are greyish-brown, with a bit of white. The small vestigial wings are used by males in mating displays. They can also provide shadow to the chicks. The feathers are soft and quite different from the stiff airfoil feathers of flying birds. They serve as insulation. There are claws on two of the wings' fingers.