Ours does that too, Ebbie. When he occasionally misfires and gets a stalk or prickles there's a lot of sneezing and snorting to get things cleared. I think that's how I first realised they were doing it.

My two acres or so of picking patch adjoins my property and is an overgrown area of mixed grass and scrub with blackberries and wild roses growing over. It used to be part of the infield when my house was a working farm.
We have travellers (Roma, mainly) in the area who use it to pasture tethered horses at times in spring and autumn when they're coming through, and that keeps some of the grass areas clear, and fertilises the blackberries etc. Other times of the year it's a dog exercise area.

More blackberries yesterday, and another 7 lb of jam - I reckon there'll be pickings for a week or so yet.

Paws