It is always amazing to learn how different species work together. A recent study showed that grey squirrels listen to the chatter of birds to determine if there is danger or if it is safe.
Anyone who watches birds at a bird feeder will recognize the chatter of birds that are content and feel safe. Squirrels also respond to bird chatter to see if it is safe to raid the bird feeder or forage in the area. If the birds react to danger, the squirrel also reacts. By the same token, if the birds return to their normal “all is safe” chatter, the squirrels also assume it is safe.
This brings up interesting questions about how many other animals communicate in this way. I have noticed a difference in my pet budgies reaction to the safe chatter of songbirds when I have a window opened. They seem to chatter more then when they are by themselves. The only other time my birds are as vocal is when they like the music I am playing. Interesting to say the least.