It's that time of year, nest building. The hawk nest building routine is on earlier blogs. I've seen robin nests. They're small cups of mud attached to a branch. This robin was collecting an incredible assortment of materials and flying it all way up into a tall pine tree. Master duplex for a change?? The squirrel's nest hole is way up a tree in a leafy field. I don't know where the sparrow is living, possibly a local traffic light cross-bar.