Here in Tokyo there vast numbers of very large and very loud crows.
Some  ornithological estimates from 2008 say there are approximately 150,000  crows in Tokyo. I would assume there are a lot more now.  
https://www.nytimes.com/2008/05/07/w...a/07crows.html
Crows are very attracted to mayonnaise (no idea why) and it is used to bait traps.
I  have found they really dislike laser pointers being directed at them  and  they do not tend to return once the light has been directed at  them.
Not sure if it would work with Canadian crows or magpies.