What does Darwin's Rhea have at the end of each wing?

Rhea pennatus (Darwin's Rhea, syn. R. darwini) is 90 to 100 centimeters (3 ft to 3 ft 4 in) tall, and has larger wings than other ratites, enabling it to run particularly well. They can reach speeds of 60 km/hour, enabling them to outrun predators. The strong claws at the end of each wing are effective weapons.

The males of this species become aggressive once they are incubating eggs. The females thus lay the later eggs near the nest, rather than in it. Most of the eggs are moved into the nest by the male, but some remain outside, where they rot and attract flies. The male, and later the chicks, eat these flies.

Outside the breeding season, Darwin's rheas are quite sociable: they live in groups of from 5 to 30 birds, of both sexes and a variety of ages.