These photographs were taken a couple of days ago on the Leadhills (Hopetoun) Estate in South Lanarkshire. They show three propane gas guns set out on the grouse moor (one inside a grouse butt).
These gas guns are routinely used for bird scaring on agricultural fields – they are set up to produce a periodic booming noise to scare pigeons, geese etc away from crops. The audible bang can reach volumes in excess of 150 decibels.
Can’t imagine why they’d be deployed on a driven grouse moor during the critical stages of the hen harrier’s breeding season, can you?