More studies

http://informahealthcare.com/doi/abs/10.1080/15368370701410558

This is a summery of a study into the theory that electromagnetic radiation from radiation, from phone antennae, either on it's own or as a part of a combination of other things, potentially affecting sparrow population. This makes sense if you consider the theory that birds navigate using electromagnetic waves from the planet, or maybe it's interfering with they're brains because of the small size (as electromagnetic radiation affects ours). This is something interesting to think about, even though I don't have access to the whole article, and it shows that there are a lot of theories about the decline, and some very obscure ones.