What Are the Saccatas and Why Do They Chirp?

There has been a lot of saccata chirping recently. And apparently they've evolved for that so that the different populations minimize the amount of time that they're out at the same time trying to compete for the same food source. So why do they chirp? Are they chirping to say, come and find me and be my friend and we'll get strength in numbers? Or are they saying, I want to love you very much in a special way?