Recreational UAS pilot reported an NMAC with a delivery UAS during flight. The recreational UAS pilot took evasive action to prevent a collision.

Narrative

Took my drone on a short flight to make sure the battery didn't go bad from not being used. Ascended to approximately 390 ft AGL and then started descending. I heard a sound I recognized as a delivery drone approaching and immediately arrested the descent while I looked for it. Within 10 seconds total it was passing directly overhead at maybe 200 ft AGL.Not knowing where it went to as I lost visual during its descent a couple streets north; I decided to hold position and wait for it to return. In less than a minute it flew underneath my drone which I captured on the camera.The drone was flying much lower than I had seen them in the past. Because of this; I had almost no opportunity to make visual contact and avoid its flight path. I believe that if I had not stopped my descent upon hearing the drone; my drone and the delivery drone would have been at nearly the same altitude and location. I understand the delivery drones have advanced sensors and are able to avoid manned aircraft. Would it have avoided my tiny drone?To prevent becoming the first person to take out a delivery drone in flight; I will be refraining from any more flights except for low altitude and more rural locations.