I can't say for certain but this may be due to Blackbirds 'Kamakazi' habit of flying low across roads particularly during the breeding season.

Been driving along the A6 Manchester/Stockport/Hazel Grove the last few days and noticed many dead birds in the road look like hooded blackbirds or starlings?? am thinking this is unusual? Is this the result of the heavy snow, starvation. Feeling very sad :( Anybody else noticed?