Surprise - the case is isn't closed. On my two recent visits to New York, I saw sparrows - in the busy 46th street, right outside Grand Central Station and on the equally busy 6th Ave. I checked my mobile phone, the signal was strong and there were about 20 WiFi hotspots - enough radiation to cook anything that crawls as per our theory. The crawling, walking and flying beings were all there and busy. I didn't want to look like a tourist in the big apple and so I didn't bother to take a picture as a proof.
So, I had to throw our theory out and look for other circumstantial evidence. Back in India, the chirping of birds wake me up; the chirp of the sparrows is missing for the past 15 years, but the caw of the crows was getting louder. The crows have become fairly aggressive and intelligent during that period. The population of the crows has gone up during this period with abundant junk food and total absence of any predators. Some hotels do consider this when the broiler chicken is in short supply.
The crows and sparrows have coexisted in this part of the world sharing the space with humans in the cities. While the sparrows thrived on grains and small creatures like insects and worms, crows got bigger sized food. Better packaging has resulted in less grains in cities; less open space causes reduction in smaller creatures. But the food for crows has increased manifold. We create more garbage with bigger chunks of food, which is good for crows. There is more food, and there's just right kind of trees to support crows - and not eagles which are natural predators to crows.
Crows are natural bullies, with an increased crow population, lesser animals like sparrows struggle to survive. And so...
But what about Manhattan? There are more parks to support predators for crows to survive; garbage is covered, leaving little scope for crows to crowd and harass sparrows.
So, when you use the mobile phone next time, don't feel guilty for the sparrows. But you must feel bad for felling the trees to make room for your apartment and when you throw food out.