I've heard conflicting and somewhat vague numbers on bird deaths. But they all seem to agree that a lot of birds are killed by flying into windows. Some reports estimate almost a billion. And that number would make windows the number one cause of bird deaths. *
again nothing definite but It appears that high rises are not the biggest problem - but one story buildings are more dangerous. Maybe because there are more of them or maybe because there are more birds flying around closer to the ground.
* I became interested in this just last week when Donald was talking about how bad windmills are. Comparatively speaking, windmills are not that big a deal.