As a child I was once told by an old 'keeper that the best way to catch a rabbit was to hide behind a bush and make a noise like a lettuce. If you think about it, it makes sense
Calling foxes in quite close can be relatively easy. The squeeking, squealing sound you are trying to imitate is that of a mortally wounded rabbit. Anyone not familiar with this would probably be amazed at just how loud and piercing a rabbit can squeal when in this situation. The fox comes close to investigate the possibility ofan easy meal. Methods I have known to work include sucking hard whilst pursing your lips in a "kiss" fashion, sucking against the back of the hand or forearm, or the most effective way I've seen is to scrape a section of expanded polystyrene packing foam along either the bodywork of a vehicle or the side of a polished gun-stock.
The squirrels coming close to Bill Oddie when he rustled his nuts in a bag (ooh-er missus!
) only did so because they were used to being fed by people. Try it in woodland where the quirrels are more used to being persecuted by the 'keeper or forrester and you won't see one for days.
I have managed to call magpies in close enough for a shot by shaking an old fashioned wooden matchbox hard whilst it contained about half a box of matches. It makes a sound veryt much like the "Chak-a-chak" call they make as either an alarm signal or whilst mobbing something. Other magpies will often come closer to investigate, especially if there is an owl or crow decoy on a fence post close by or a dead rabbit laid out on the ground.