Why do cuckoos cuckoo?

[werdnal]

Probably thick questions!

We have had a cuckoo calling regularly this year, usually morning and evening, and although the traditional rhyme suggests they stop in June, he was still going stong tonight! I know its only the males who have the cuckoo call, but do they call to attract a mate or is it territorial to keep others out of their patch? Also, as the cuckoos take no responsibility for raising their young, does a pair stay together for the breeding season, or will the male call various females into his patch, to mate and lay. How many eggs does a female produce in a season?

Thanks