Can anyone explain how the BGBW statistics are collated/calculated to produce a 'true' picture? Different times produce completely (for my garden certainly) statistics.
Today (Monday) at noon there were 3 male blackbirds fighting over 2 females; 2 coal tits (unusual); great tits and blue tits (regular); more sparrows than usual (lots) and the collared doves and wood pigeons showed up on cue. On Saturday at the same time for forty-five minutes of my hour there was not even any song! (luckily my wife had done her hour earlier so we were able to submit 4 [rare for us] longtailed tits along with the usual suspects). Even more extreme - some weeks ago, 5 redpolls. Not even identified until I considered, "sparrows don't hang upside down eating birch seed and they're not tits." Not seen before, or since.
We used to get goldfinches, now we don't, that's a measurable statistic. But if a Golden Eagle had visited our bird table would that have been a statistic? The redpolls? But you get my point. How does RSPB weight the sightings? Comparison with earlier years (for an area)? Averages? I'd really like to know.