A keeper mate of mine told me how he used to trap magies when the numbers got out of hand,
Build an 8 foot circle using chicken wire and fencing stakes, tie a ladder across the middle of the circle on top of the wire, then use more wire to go from the sides of the ladder to the sides of the circle.
Bait the inside with eggs, dead rabbits and shiney things and leave over night.
He said the maggies curiosity gets the better of them - they fly around it, eventually landing on the rungs of the ladder, and drop down to eat or steal the shiney things. But when they try to fly out, their wingspan is greater than the space between the ladder rungs so get trapped inside. You can then deal with them in a confined space by whatever means suits - though he did say to wear goggles if you tried to get in the trap as they tend to go for your eyes once they hit frenzy pitch.
Good luck RB, they're wiley creatures.
Ogri the trog