Thanks Geoff. It is very interesting.
Perhaps some statistics could be used to make the analysis more meaningful.
Also, there should have one bias - submission of records. Some species are common and so many birdwatchers would think no need to record or provide information of it, while other species which would be rare before were actually required submission of records. So, it sometimes make a situation that rare species have more records to show trends but common species do not have enough or meaningful information to show trends.
