LOS Conservation Officer Roy Rhodes has provided this link to the LeighLife website on which there is information by Tom Edmondson about the history of birding in the Leigh area from his perspective.
On the same website there is also a collection of photos and cuttings about the chequered history of Pennington Flash and the flooding which used to occur and that seems relevant too. There is also a section on what was then called 'Astley Flash' east of the tip at Astley Green.
I've only scanned it at present, but I think I'll be printing it out as it looks a really interesting read to find out what the birding and habitat was like in the past. Here's the link again to make sure you don't miss it!
Ornithology and Conservation in the Leigh District 1938-1956