Estimating Starling roost numbers

It's very difficult estimating the numbers entering the roost at Middleton Moor, birds are flying in almost constantly during the hour before dark. The birds almost immediately enter the reed bed with no real pre-roost flight. I can see why estimates are as high as 100,000. The photo below was part of the largest single group which could by 5,000 birds, the sky darkened as they went overhead. 
Whatever the number its a real spectacle.

Starling flock