At first sight, these two seem to be uncaring of the other's presence, but that was short lived. The Chipping Sparrow has its nest in the bush right there and wants the chipmunk (aka Mr. Chipper) no where near this bush or railing! It was quite entertaining watching as the sparrow chirped at the chipmunk and jumped toward it to show its displeasure. Eventually, the sparrow jumped on the chipmunk to let it know that it had come too close to the nesting area. Mr. Chipper finally got the message and high-tailed it out of there.
You can learn more about the Chipping Sparrow at the Cornell Labs website, including hearing their calls. To learn more about Chipmunks, you can visit the Hinterland Who's Who site.