This was after I moved towards a repeated strange noise that sounded like a cross between a mallard's "quack" and a crow. It was a sort of "quawrk" sound.
black crowned night heron roosting
It took me a few moments to realise I had stumbled upon a day time roost of a very large number of black crowned night heron.
first wave of night herons moving
They had been sleeping in a few trees and tamarisk bushes that grow inside the edge of the reeds. Over 30 birds flew out. However it didn't stop there. A second wave of about 20 birds shot out about 30 seconds later.
third wave of night herons moving
I then starting to walk on down stream, past the place and to my great surprise after I had walked on a few metres away from the bushes a third and biggest wave of 53 birds left in the opposite direction to the other two.
In total there were over 100 black-crowned night-heron in the roost. The big majority were adults.
Anyway the good news is that once I was safely 50 metres or so away they returned to the same place and disappeared from view.
I didn't capture events well on camera because I was continually caught by surprise.
I am left wondering if this sized flock is usual? it was certainly the first time I had seen so many.