Channel Billed Cuckoo Behaviour?

For a while Ive noticed a group of channel bills flying over doing circuits of my area making their call. However, over the past few days theyve been behaving differently. There are now three of them, and instead of only coming in early morning, I see them in the evening too. There seems to be one that the other two follow, and Im wondering if that may be a female and the other two may be males?
Also, when do they leave for Indonesia haha Im sick of them.