US Army, Cessna O-1G Bird Dog
Cessna O-1G Bird Dog, US Army at Planes of Fame Air Show, San Bernadino County, Chino CA.
The name Bird Dog was chosen because the role of the army's new aircraft was to find the enemy and orbit overhead until artillery (or attack aircraft) could be brought to bear on the enemy. While flying low and close to the battlefield, the pilot would observe the exploding shells and adjust the fire via his radios, in the manner of a bird dog (gun dog) used by game hunters.
Canadian Aviation Blog