A feature of any walk around the Millennium Green will always be the myriad of bird songs to be heard, even if the songsters cannot be seen. Becoming an expert in identifying birs from their song alone requires many hours of listening to recordings and walking the ground, something not all of us can devote to the task.
Why not use the RSPB’s handy online guide to the calls of the more common species such as these below, to be heard around the Green in the Autumn?
You may also be interested to try the RSPB’s “Find a Bird” facility that provides both aural and visual identification assistance.
Ashton Keynes Millennium Green 