Yes, rowan, some robins we see in Winter are migrants from Scandinavia, here to avoid Scandinavian weather. But I don't think LEAF's survey permitted of an answer "some don't" , which meant "some we see are Winter visitors" or, as is the case, that some of our female robins cross the Channel !
Ed, LEAF encourages organised farm visits, but you're right to suggest that 'Townies' can be a nuisance to farmers. Actually, the worst 'offenders' are people who come to live in the country. We had one man who complained that we should clear cow muck from a cattle path, because his children were getting it on their shoes when the walked through to play in the cow pasture which it led to. And the number who think a wood, a mile from the road,is a public park, together evidently with the fields adjoining,apparently on the grounds that it has a pretty river in it and some others like them walk in it, is quite large. I've more than once had it asserted to me, when I've stopped a dog walker or picknicker, that "It's public". Pointing to the fields of arable they've crossed to reach it doesn't dissuade them from this opinion.