Questions for vegetarians?

This isn't supposed to be bashing vegetarians but it did come across my mind. Many people say they are vegetarians to stop animal cruelty, but when farmers harvest grain many birds and small animals are killed or have their homes destroyed by the harvesting machines. Also in order to have more crop farmland trees are destroyed thus destroying acres of habitat and cause many species to become extinct or endangered (this can be seen every day. Where I live the whole area used to be forest or natural prairie gr, now it is all corn and soybeans). Don't you consider this cruel to animals too?