Disappearing birds.

Okay, I'm new to this - the BGB not an interest in birds - but it seems to me that perhaps the activity could take place over a week rather than just two days. So many people are commenting on the fact that today's very windy and somewhat wet weather conditions led to a huge reduction in sightings today compared with yesterday or indeed virtually any time last week and I would certainly agree with this. I chose to complete the activity today when the maximum number of birds seen at any one time was just five (blue tits), followed by four in the case of chaffinches, blackbirds and house sparrows. Had I done the 'audit' yesterday I know there was a time when there were sixteen chaffinches and a dozen house sparrows present. It seems to me that having such a small 'window of opportunity' which can be so easily ruined by the weather actually brings the validity of any 'findings' into question. I know the results I gathered today are not indicative of the amount of bird life in my garden and wonder whether allowing the activity to take place at any appropriate hour during say, the last week of January, would lead to more reliable results. On a more personal note, has anyone else noted the dramatic decline of long tailed tits this year? I'm aware that populations move and change and hopefully that will be the explanation but for the last two years my garden has been alive at this time of year with groups of these beautiful little birds whereas this winter I doubt I've seen more than two or three.