DAVID FROST says: Pheasants, even reared ones, are counted as wild birds and they belong to the person on or over whose land they happen to be.
If the bird falls dead over the boundary it belongs to the neighbour, even though it may have started off on your land.
If you try to retrieve it you are technically poaching and if you were to cross the boundary with your gun you would be guilty of armed trespass.
Ideally shoots should come to an agreement with their neighbours about what to do in these circumstances and the rules should be made clear both to Guns and pickers-up.
On one shoot where I regularly pick up, there are three drives where the pickers-up are over the boundary and reciprocal arrangements apply when the neighbours are shooting.
Sensible landowners and keepers should be able to make things like this work.