Corvid Cleaning in Sweden: https://corvidcleaning.com/

Apparently got scooped by the media - not ready to share yet.

Puy de Fou Park in France: More of a stunt than a sustainable effort, but very cool.

The Crowbar by Crowded Cities: https://www.crowdedcities.com/

Wishful thinking by a Dutch Startup. Design looks nice but does not appear very functional.

The Crowbox: http://www.thecrowbox.com/

Open source project based on a Dutch entrepreneur's idea. Latest version ncovers food instead of dispensing it.

Original Version

Current Version

The Crowkit: Looks like an old, discontinued project. There is footage of crows using it as intended.

Hans Forsberg: https://www.youtube.com/channel/UCtkv3wuEP-Veur4iYJWkBgA

Real accomplishment getting wild magpies to exchange bottlecaps and other items for food. This project really got me started on my own. 

Tomas and Olof Morsing (The Magpie Recycling Project): https://www.youtube.com/channel/UCEhPdSIMrLNynfwnkibVzZg/videos?view=0&sort=da

Other than Forsberg, one of the few successful examples out there. Huge contraption, but if I had my own yard I'd build big too :)

In the end, for the purpose of getting wild, untrained birds to exchange stuff for food, the only the  success in getting wild birds to exchange litter for food I've seen so far was had by:

• Hans Forsberg
• Tomas and Olof Morsing
• Some builders of the Crowkit