Elsewhere on Portland there was the loitering pair of Black-necked Grebes at the Harbour and a single Black Redstart at Reap Lane.
Although we now know from sound recordings sessions that Moorhens are relatively frequent nocturnal migrants here, daytime sightings aren't even annual and the species is notoriously tricky to see when it does pitch in. Today's bird at Culverwell wasn't even glimpsed despite being audible at close range (in just the sort of spot where you thought you couldn't possibly not have seen it) for extended periods throughout the morning - we even had to go to the lengths of sending a recording to Joe Stockwell and Nick Hopper for them to confirm that it was indeed a Moorhen!
As an aside, Joe mentioned the difference between these calls and those given in flight by nocturnal migrants - we'll have a look at that another day when we've got a bit more time.