My brother in law and I were talking about this the other day. We all live on the same piece of property and there is one long driveway leading to each of our houses. If there were some kind of confrontation at one of the houses we have a particular gesture that could be seen through a scope if “back up” was needed.
I have another prepper friend that I am linked up with and we have a code word to let each other know if SHTF is going down in our neck of the woods. The bird code you used is a good idea. Code words need to be non-descript and simple so as not to tip some unwanted listener off.