We walked for hours in the shade of these plant vaults that scarcely let us catch glimpses of the blue sky, which appeared to be more of a deep indigo blue because the green, verging on brown, of tropical plants seemed so intense. A great fern tree (perhaps Aspidium caducum) rose above masses of scattered rock. For the first time we saw those nests in the shape of bottles or small bags that hang from the lower branches. They are the work of that clever builder the oriole, whose song blends with the noisy shrieking of parrots and macaws. These last, so well known for their vivid colors, fly around in pairs, while the parrots proper fly in flocks of hundreds. A man must live in these regions, particularly the hot Andean valleys, to understand how these birds can sometimes drown the noise of waterfalls with their voices.