I’ve seen some of my males chirp at any time of the year. It tends to be when they are alarmed by something, and could be to warn the others of danger. They chirp very loudly and quite fast, but not for very long.
Then sometimes they will chirp for no reason I can work out. This is a much slower and softer chirp.
I should say that the females can also do this as well, I have only noticed the females do that constant all day chirping though.