I don't always think it's the best to mess around with nature. Somehow, it mostly seems to sort the problems out without our interferance. Magpies were a problem here a few years ago, then came the crows both have diminished again. The fact that buzzards have been introduced back into the area by RSPB is now having it's effect on other species.
Hedgehogs are at a considerably low rate, due to gardens being fenced off, they are unable to travel, and eating slugs that have been fed slug bait kills them too. Swallows were almost nil last year in comparison to previous years but they return generally to the same area and their habitats are being destroyed.The owls, which I think improved after almost extinction in the area a number of years back, although I don't know how they are at the moment. Of course, as we all know the little birds are dwindling,no hedgerows and are they are probably being caught by the hunters.I had a number of dunnocks which came regularly for food in my garden for the previous 10 years,until about 2 years ago,I haven't seen any since. So many species are being troubled, these are just a few in a short period of time. Are you almost in tears? I hope so
Squirrels, I would let them sort themselves out at the end of the day, the garden is their home, more so than ours.