There were 3 or 4 of these swooping and darting around, landing only briefly. Catching them in flight was beyond my skills with the 150-450mm, but I did manage to capture a very small no of decent shots while they very briefly landed and stayed still for a second or two.
Once you have the time to look at them, you find they have a very interesting set of colours and markings.
(Actual Shutter speed was 1/1600s but that setting was not available from the drop-down Shutter Speed list)

[MikeNArk]

Nice capture of the bird. Looks good on the beach rock.