This blog has been stuck in the 60's and 70's for a while now, so I'm going to back a lot further with this one. It's Chester A. Reed's 1916 Bird Guide: Water Birds, Game Birds and Birds of Prey. Reed produced a series of pocket sized (3.25 x 5.5 inches) in the teens, they appear to have gone into many impressions, as I have other books from the series from the 1930's. They must have been among the earliest full color bird guides. The illustrations measure 2.5 x 1.5 inches and have a matchbox quality to them.