A study has shown that different species live in mixed flocks so as to use each other as sentinels against predators - how smart is that?! But it doesn't only happen with Amazonian birds - look at the second and third links for Australian species that do the same thing.
https://www.sciencedaily.com/releases/2 ... 170044.htm
https://www.zmescience.com/science/biol ... -242789930
https://www.zmescience.com/science/aust ... -242789930