I've seen grackles in Austin, Texas, USA do something similar around one of their own that had flown into a window and was badly stunned. It did seem to preven

I've seen grackles in Austin, Texas, USA do something similar around one of their own that had flown into a window and was badly stunned. It did seem to prevent any feral cats or other predators from being tempted to come by, and the noise might have been an attempt to wake up the stunned one (who wasn't there when we came back from lunch, so I assume survived).