I agree w/Rod. HOWEVER, in my municipality, it's illegal to 'transport' a wild animal, squirrels included.
If you invest in a Have-A-Heart trap AND a good pair of Electrical Lineman Gloves, you can catch them. Just put the food in them that they've been eating, and you should be able to catch them. IF you find the food has been eaten AND the trap didn't go off, you need to check the 'linkage' to see that it isn't hangin up on anything, or, adjust the 'hook' that holds the door open. Also, it's possible that the food may be gone AND the door is closed! If this is the case, they may be able to squeeze out between one of the few small openings in the cage. The BIGGER traps are for cats and 'coons and such so they have relatively 'larger' openings in the cage that may allow a squirrel to get out. On the other hand, the Small Rodent Trap doesn't have these 'bigger openings'. (I opt for the larger trap because you can catch, well, larger animals if the need arises.) IF the squirrels are squeeeeeezing through the openings in the cage, you can 'wrap' it in some chicken wire.
Try to set the trap AWAY from the garden, best between the direction they're coming from and their destination. (Between the nest in the tree and the garden.) They don't weigh that much so the 'plate' needs to be sensitive. Sometimes, I put small, but 'large', pieces of wood inside so they have to jump and hop a bit to get to the food. This way, you can 'force' them to take a certain path INSIDE the trap and thus, set it off. Also, lay in a piece of thin wood or cardboard on the BOTTOM of the trap. Walking on that wire is VERY uncomfortable on their feet!
My best to ya and hope this helps.
PS: WHen you catch one, set the squirrel, TRAP AND ALL, inside a trashcan that has been layed down in the back of your car / 4x4 / whatever. Bring a coathanger w/you and when you get to your destination, set the trap down. Use the coathanger to 'open' the trap door and hold it open. Then, entice the squirrel to leave. DO try this out BEFORE you catch a squirrel so you can see if you can do it, or if you need another 'tool' to assist you in opening the trap. Have fun with it, and DON'T let anyone see you catching OR releasing the squirrel. All 'they' need to do is write down your license plate # or take a photo or something, and you can be fined! I've done this with skunks with 100% success. Remember, test opening the trap up BEFORE you bait it, and put a piece of cardboard or something in the 'front' part of the trap (before the trip-plate), and be sure the door 'hook' is sensitive for their light weight.