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At the moment I have a colony of these nesting in my back yard! They scare the heck out of me, (they are huge!) but I had heard of their declining population before and did not want to contribute to it by offing them so we have a circle of grass that is quite taller than the rest of the yard...

I am sure there must be a way of moving their nest out of your area without eliminating them all!! We had a hive on our balcony and moved it and the bees moved too!! That is surely not anti environmental? Try finding someone who knows about these creatures and consult them. There are people in Spain who breed them to produce honey in the orchard tree areas and in the hills where there are herbs which help produce delicious natural honeys.