OK I still have not sorted out the plug ins to get Xeno Canto embedded but my thoughts on House Sparrows. They are brief so this 24 sec extract may be longer than it takes to read this.
I do not have enough data to prove these views but Tratalos et al (2007) looked at 27 urban indicator species across housing types. They show an increase in House Sparrow numbers until the most densely populated housing at which point there is a sharp decline. This seems to be true across the tetrads I have looked in. However, something else I have noticed again it is anecdotal is that the tetrads I have found the most House Sparrows have also been the ones with the most Collared Doves. C- Benwell and E-Kenton Bar being good examples. I am not saying this is cause an effect, but it was really noticeable.
The BBC claim that it is the effect of house insulation that is the problem. House improvements may have an effect on reducing nesting spaces, but there will be a lot of interlaced factors. Kurt showed there is not much movement between flocks in winter. In what I have seen these flocks are unevenly distributed and centre on a hawthorn hedge, clump of ivy, privet or leylandii. Only one of these would provide the insect food that Vincent has demonstrated that sparrow chicks need before fledging. So food, nesting and winter flocks all become issues.
In addition our garden House Sparrow flock now seems to be down to two pairs. We have post fledging had 20 plus which has made the crowded and exciting in equal measures. These four birds are out-competed for seeds by 9 Greenfinches, 2 Goldfinches and 2 Chaffinches. There are lots of complications if we want to hang onto House Sparrows. So if you are considering planting a hedge plant Hawthorn and put up a sparrow nest box if we want to hang on to the chatter above. Incidentally, you will notice this is not a British recording. When was the last time you saw more than 50 House Sparrows in a flock?