Despite there seemingly being lots of churring males in the county in May, I get the impression that it hasn't been a very good breeding year for them? At this time of year, Nightjars should be incubating or have fledged a second brood by now, and their first brood should be well on the wing, if not fully independent! At the 3 'new' sites that I found earlier in the year, which had at least 10 churring males between them, I have only managed to find breeding evidence of one pair - a sitting female (pictured below), presumably still trying to raise a first brood as there's no evidence of any juvs on the wing.
I hope that I am wrong, but my guess is that they have struggled this year!!