This pair of photos contrasts the ostrich, the largest and heaviest of all living birds, with the house sparrow, a small bird weighing less than 40 grams. Part (a) shows two adult ostriches, a male and a female. They have a relatively small head, a long, bare neck, large body and long, sturdy legs. The male has black plumage with a white tail, while the female is grey-brown in colour. Part (b) shows an adult male house sparrow in breeding plumage. It is dark grey-black on the crown, around the beak and on the throat, and is chestnut brown at the back of its head. Its cheeks and underparts are pale grey and white. Its upper back and mantle are a warm brown colour with broad black streaks, while the rump is greyish brown.