Researcher: Vegetarian Diet Kills Animals Too - ABC News
Basically, to summarise the article; when fields are prepared for crops, the farmers kill several wild animals in order to do this. When a field is to be planted with crops, the habitats of animals are disrupted far more than if cows are put there. Also, farming methods kill wild animals; not just machinery, but also pesticides, too. Therefore, there is no point in vegetarians and vegans smugly saying, "Well, at least my diet ensures that no animals are killed," cuz they are causing the deaths of animals too.
Note; this is not an attack on vegetarians or vegans; merely an observation. If you choose to be veggie, great; just don't make wild statements or condemn those who choose to eat meat.