I don't think so. There are indeed plenty of buzzards hereabouts, and it's not uncommon to see five or more soaring in the summer sky in a loose ensemble. But buzzards are lazy buggers. They will go for carrion and slugs and snails as much as for live prey. We have plenty of buzzards around here, along with more mice and rabbits that I care to contemplate. So the grub is there. Must be some other explanation.