What? A dove carrying a brick?
It’s a simple question of weight ratios! A five ounce bird could not carry a one kg brick of gold!
Maybe the bricks could migrate?
He carries one of the bricks across the bridge to his assistant (He’s a magician…he’s got an assistant), gives it to him or her, then goes back and gets the other two.
Supposin 2 doves carried one together?
No? They’d have to have it on a line…
Since the rules of the question forbid the magician to throw the bricks, juggling is disallowed anyway.
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Marc.
Two doves could carry it on a string!
Damn. My joke was already taken 
Are we talking about African or European doves?
Everyone’s assuming he’s that other kind of magician.
Here’s some answers for the real kind.
[ul]
[li]Turn into a dragon and fly over.[/li][li]Reduce the mass of the bricks or himself.[/li][li]Teleport.[/li][li]Cast a spell of strengthening on the bridge.[/li][/ul]
Can’t the greedy git just leave one behind? He’s already got 2 gold pieces, dammit! Not bad going for a magician that doesn’t even have a car…
The problem as stated doesn’t specify that you have to cross only once, so the easy answer is, as already mentioned, taking one brick to the other side, going back, and bringing the other two across. It’s a lot easier than juggling gold bricks, isn’t it?
If he’s a magician, he should have no trouble pulling a rabbit out of his hat. A 1 kg rabbit. Now he can just walk across with his gold. He’d better tie the rabbit up first, so it doesn’t try to follow him across.
While that's a traditional trick, not all magicians approve of using animals on stage--thus not all magicians are going to be skilled at pulling rabbits from hats.Bundle up the bricks in your shirt.
Tie the string to the bundle.
Walk across the bridge.
Pull the bundle after you.
Ta Da!