Be wary of squirrels taking over your garden - I felt that way when I first started feeding the birdies, about three months ago.
I got quite fed up with the squirrels demolishing peanut feeders (4 of them ranging from plastic to reinforced stainless steel - no job too large, it seems) so decided it would be fun to give them their own feeder.
This worked amazingly well for a while, but it got to the stage where the squirrels were outnumbering the birdlife, and still tackling the bird feeders (although less so than before). One morning I looked out and I had seven of them. Doesn't sound many but if you were to see the size of my tiny garden you'd appreciate this was a hefty furry critter:acreage ratio. In addition, their presence was attracting stones from the neighbours and stealth 'attacks' by domestic cats who quickly cottoned on to the fact the squizzas were using Clayts' garden as a snack stop.
Hence why I removed the squirrel feeder (and had to draw the curtains to avoid the looks of disappointment and confusion on my furry friends' faces) and set up a new feeding regime on the edge of the woods - I still get to see them, but not all in my garden. This also means they have a faster exit to their natural habitat when the hopeless and inept domestic cats attempt an attack, plus they're not getting caned by the neighbours (how anyone can do that is beyong me).
I've read supposedly scientific stuff saying squirrels aren't territorial. From my layperson observations of these charming animals I have to disagree - between them they squabble, chase each other off, get grumpy with some of the bigger birds (woodpigeons and magpies especially), but do bow to the might of the collared dove who, despite being little fellas, regularly slap magpies, woodpigeons and squirrels down.
In terms of their relationship with our local sparrowhawks, I've seen two squirrels on a fence flanking a sparrowhawk with no ill-feeling whatsoever - they seem to rub along okay.
Generally, squirrels are fairly genial creatures - clever, witty, engaging, mindcrushingly cute, but also devious - and rub along fine with the little birdies here. A couple of them are also quite chummy with me now, and don't run off when I'm about - we're not at hand-feeding stage yet (and neither will we ever be : they're not pets after all), but they have learned to trust me - indeed they now wait for me on the fences by the wood to do their 4pm feed and pounce as soon as the first peanuts hit the deck.