It is true that small wild animals are killed by pesticides and inadvertently by machines during harvesting.  It should be noted that the majority of the grain grown worldwide is used to feed animals – not humans.  So going vegan would help to reduce the number of small field animals killed in this way.  If we want to completely eliminate pesticides and large monocrops which use harvesting machines then vegan organic farming is the solution.  For an example of this see: Tolhurst Organic.