Grassy cup bird's nest

A bird nest is where a bird lays its eggs, incubates them, and raises its young ones. Although the phrase is sometimes used to refer to a specific structure built by the bird itself—such as the grassy cup nest of the American robin or Eurasian blackbird, or the beautifully woven hanging nest of the Montezuma oropendola or village weaver—this is an overly narrow meaning. 

For some species, a nest is simply a shallow depression dug in the sand; for others, it is the knot-hole left by a broken branch, a burrow dug into the ground, a chamber drilled into a tree, an enormous rotting pile of vegetation and earth, a shelf made of dried saliva, or a mud dome with an entrance tunnel.