This was written way back at the turn of the century. Long out of print, they are excellent observations of birds that is very hard to read about now. Any of this series should be owned by serious or even casual birders.
Though I've yet to wade through all 3 volumes, its fun to read all the old accounts of bird behavior in these Bent books. As my Ornithology instructor replied when I asked him what book was the best reference for bird behavior... "Get Bent!"