The estimate is 16 to 42 million birds die each year from hitting glass. On the low end, each building (of which there are 15.5 million in Canada approximately [source]) on average one bird dies due to hitting glass per building. That is not quite in the realm of ‘piles of birds around every low rise building’, given that they do not occur all at once (it is an annual number after all), and the bodies do decompose, get eaten, or get cleaned up.