Has anyone ever tried measures to flush incubating hens or leverets from the front of machinery during mowing operations? Flushing bars are used to avoid killing incubating hens and mammals in north America. They consist of bars with hanging chains fixed to the tractor and hang over the uncut crop in front of the mower. See http://www.ducks.ca/province/ns/how/ground/flushingbars/index.html for more information. Would be interested to hear if anyone has used them or anything similar with any success in the UK.
I can only comment on corncrake, where we used dogs, flushing bars, rope dragging and terminal imagery to either locate nests for ringing/pre-cutting, or with cutters. Short story is the birds sit tight, hence the emphasis on delayed mowing to protect first and second brood nests, and friendly mowing in strips or centre out to protect adults and young. Somewhere there will be papers backing this up!
Interestingly, someone told me recently that mowers designed for the first Massey Ferguson tractors – which were just cutting bars – had wildlife flushing bars on them. He seen vintage versions with them.