Trimming a native country hedge out in the field is very different compared to clipping your garden hedges.
Because most country hedges are trimmed by a tractor mounted flail, perhaps like this:
It’s no bother to trim on a two or three year cycle, which is cheaper, and much better for wildlife.
Several birds won’t hang around hedges that are trimmed yearly: they need the cover of long branches that arch up and out.
Grazing animals are often unofficial native hedge trimmers, which may be cause for a barbed wire fence.
The cover image below shows Regenerative Farmer Ben with a section of laid hedge that has been browsed clear at the base; towards the end of the video, they show how installing a little fence allows it all to regrow.
When in the Year to Trim Hedges for Wildlife & Birds
For wildlife overall, the perfect time to cut when the branches are bare of berries, well after the leaves have fallen.
For nesting birds, it’s late February to September that matter; in most places it will only be pigeons nesting after August.
The official recommendations are not to cut hedges between March 1 and August 31, but the actual hedge trimming is never illegal, destroying bird nests.