I take it the shotgun used to scare the birds were firing some of these and not just standard cartridges.
https://www.wildlifecontrolsupplies....NWS15MMBB.html
I am surprised in this day and age they do not have something built into the ramp similar to something like this
https://portek.co.uk/portfolio/scatt...aring-gas-gun/
rather have three men and a shotgun having to walk down the front and let rip with a shotgun.