Tell us about yourself!
This is already being done with crows- see link to an amusement park in France that has a murder of crows that pick up cigarette butts - http://mentalfloss.com/article/554401/trash-collecting-birds-keep-theme-park-clean-france.As for identifying and picking up other types of trash, see this TED talk that proposes a device that will train crows to pick up trash after stadium and concert events - https://www.ted.com/talks/joshua_klein_on_the_intelligence_of_crows/transcript?language=en
It occurs to me that a cheaper and easier alternative for the rings would be a pair of 4 or 5 inch plastic embroidery hoops, available at many craft and variety stores.
Most post office have automated mailing stations in front by the mail boxes.
Homemade Twinkie Challenge