There used to be a bounty on things like sparrows heads. Didn't make too much difference as far as I can see.
Sparrows and many other town and country species are now in rapid decline in many areas, a friend of mine has done extensive research into this, to cut a long story short, what he and a few and a couple close reasearchers have come to an agreement on is,
not only has a sparrows habitat changed that prevents them from finding suitable place to live, IE, modern buildings are hermatically sealed against entry points in which they can make a nest, it seems that there is a link to certain kinds of pollution including unleaded petrol, which is used predominantly in towns, which was developed to prevent carbon monoxide poisening is enclosed areas, or that was their main advertising point quite a few years back.
This is what these people think that is killing off the prime early food sources, you see in the early days of a young sparrows life, it is fed on small insects and or aphids, these paticular insects seem to be in decline and not enough food can be found to keep them going through this stage in their development, its like a weaning process, before they go onto the larger more whole foods.
If it is global warming that is doing it, then the signs are there already, which could effect larger and other things like insects and crops which work together for germination, once this chain reaction starts it will be very hard to stop quickly, its sometimes easy to polute an aea,but takes many decades to clean or clear up afterwards.
I myself have noticed these changes, I will tru to explain explain, when I was much younger I wrode a motorbike, and every time I went out for a ride, my visor would be totally covered with insects even on a short journies, today we still live in the same area but my car windcreen doesn't have anywhere near the same amount of dead insects on it as it used to have, even in an insect population boom which sometimes occurs, has anyone else noticed this throughout the years and or seasons.
One thing that is ironic though is, since the advent of unleaded petrol and the cataliyctic converter, the gas which was once produced by petrol driven vehicles has changed from monoxide to dioxide or C02, which is what a CAT produces once that its up to working temprature, which is now the main gas concernd with global warming.
Treat the cause, not the problem
Davy.