I didn't know this, did you?
This is something that is going around on Facebook right now.
I do know that cats have their territories, one female per territory, but a male has a much larger territory and services several females in his territory. And that is why you will see more stray males wandering around, as the young ones are trying to find a territory for themselves.
I would hope that this ear-tipping or notching is done all over the country. If you are interested, you may want to call a local veterinarian and ask if it is being done in your area.