No buzzards in Avebury, obviously, and no gamekeepers to import 'myxi'. When a person has seen a monument bulldozed - levelled - the complaints about bobtails seem rather shallow. Better to research one of the prime orientations of the greater landscape. Viz. the view over the Z-stones.
The length of the long moon cycle - 18.6 years - must have been about the age of the first child being born (generation length) so, perhaps, the two were interlinked.