BURNLEY have been made to pay for missing early chances as they go into the break a goal down.
The Clarets started brightly, with Martin Paterson looking to benefit and get back among the goals.
But when the striker was on target, he found Jack Butland in fine form.
After first sending a volley at the England goalkeeper, Paterson pulled a good chance wide.
The Northern Ireland international then sent a speculative effort wide of the angle, before being blocked by Butland after racing onto a good ball by Ross Wallace.
Birmingham, who had been forced into a late change to their line-up with Peter Lovenkrands replaced by Nathan Redmond following injury in the warm-up, settled into the game towards the half-hour.
A poor challenge by Joseph Mills on Rob Hall on the touchline led to a booking and a free kick for the home side, which was initially well defended. But when the ball came back out to Hall he duly put it back into the box, where Curtis Davies climbed to send a free header past Lee Grant.
Michael Duff had a golden chance to restore parity, but after the ball fell for him at close range – after Dean Marney flicked on Wallace's left wing cross – his cushioned effort cleared an open goal.
It needed a good save from Grant to prevent Redmond from doubling Birmingham's lead just before the break.