This is the merging of photos, or bits of photos, to create an image that could be called ‘photo-realistic’. That is enough ‘realism’ for it to be possible. This is a fine line however, because often elements are included that obviously are not real, but Photo-realistic means that it ‘looks’ like a photo.
Sometimes many different photos are combined. Sometimes it’s merely the inclusion of a bird. Often it takes many hours to produce.