Well now, it's very difficult to pin down exactly who or what is killing the birds.

Yes, some gamekeepers shoot or poison, gambling that they're never going to be caught but estates have often given instructions that they're not to kill protected birds.

With Grouse, it's difficult as numbers are at the mercy of the weather conditions affecting their food and the Heather. With Pheasants, estates rear them in large numbers and they often prefer to take the hit from hawks of all sorts rather than risk unwanted attention generated by killing such birds.

I don't know what the answer is except that it would greatly help if estates would instruct keepers not to kill protected birds of prey under threat of dismissal if found doing that.

Estates often allow "helpers" to assist in controlling vermin and they're often less disciplined than the keepers.

Also, some shoots don't have full time keepers and rely on shoot members to "do the keepering". There's often people allowed to shoot vermin along with the ferreters and the air gunners.

Grouse are in less populated (often remote) areas so there's more chance of illegal activity going unnoticed. I think the best that can be done is to contact all estates and shoot organisers particularly those where it's known that a bird's "gone missing".