When we think of a nest, we think simply of a natural piece of construction. A bird gathers together twigs and stems and leaves and assembles them into a shelter for its eggs. We don’t think much about the plants it uses. They’re just building material.

But in at least some cases, there may be more to a nest than meets the eye. It may be a cooperative breeding project, produced by two partners–animals and plants.

Francisco Fonturbel, an ecologist at the University of Chile, and his colleagues study the green-backed firecrown hummingbird, the range of which stretches across the forests of Chile and Argentina. As you can see from this picture, it builds a peculiar nest that looks as if it’s