Mark Viduka scored twice in his first start since the beginning of April to set up a comfortable Middlesbrough win.
Boro were livelier from the start and went ahead when Viduka side-footed home from James Morrison's driven cross.
Viduka was denied a penalty when Matt Upson brought him down but scored again with a stunning drive before half-time.
Birmingham pressed after the break but could not get past a determined Boro defence, and Franck Queudrue slotted in from a free-kick to add to their woe.
After the home defeat by Manchester City on Saturday, it was another performance to worry Blues boss Steve Bruce, for they looked short of attacking ideas and were shaky in defence.
Boro were solid at the back, marshalled by the outstanding Gareth Southgate, while Viduka and Jimmy Floyd Hasselbaink caused Birmingham's defence all sorts of problems throughout.
The home side were first to threaten, as Nicky Butt met a fine cross from Stan Lazaridis from the left with a firm header which Mark Schwarzer saved well.
But from then on Boro were always in control and, after Hasselbaink shot narrowly wide, Viduka made no mistake from Morrison's firmly struck cross to put them one up.
It should have been 2-0 or at least a penalty five minutes later when Viduka charged down a clearance from Taylor and, as he dithered with the goal at his mercy, he was felled by a clumsy Upson challenge.
Blues were hoping the majority of a healthy attendance, boosted by allowing in children for £5, would have plenty to shout about, but it was the visiting fans who were soon in full cry.
Middlesbrough's superiority was underlined when Viduka controlled the ball superbly from a throw-in, brought it on to his right foot and curled a powerful shot over the startled Taylor into the far corner.
Bruce was not amused with what he had seen and threw on Mikael Forssell and Muzzy Izzet at the break in a bid to kick-start his team's season.
But as much as they huffed and puffed, there was a lack of real quality and imagination in their forward play, posing few problems for the Boro back four.
Indeed, the away side continued to look more incisive and it was no surprise when Queudrue made a good run and got round the back of Birmingham's defence to meet Downing's free-kick and finish the game as a contest.
Blues staged a rally of sorts at the end, with Butt sending another powerful header just over the bar, while Jermaine Pennant smacked a free-kick against the angle of post and bar.
In the last piece of significant action, Izzet's shot was cleared off the line by Queudrue - it was one of those nights for the home side.
Birmingham boss Steve Bruce:
"It was a horror show and I'll take responsibility. There was some very poor stuff.
"We just ran out of ideas and we had too many players either injured or running on empty to cause them concern.
"The season is only three games in and I know for a fact that we'll be far better against West Brom on Saturday and we'll be ready for that challenge."
Middlesbrough boss Steve McClaren:
"When Mark Viduka's fit there is no-one better in the Premiership at what he does and the two finishes were superb.
"He is a special player, he has real quality. The first goal wasn't easy but the second was really special.
"In the first six months with us he was excellent and we were playing very well. We then lost him and struggled and it's great to have him back."
Birmingham: Maik Taylor, Melchiot, Cunningham, Upson, Lazaridis, Pennant, Butt, Tebily (Forssell 45), Clemence (Izzet 45), Jarosik, Pandiani (Gray 68).
Subs Not Used: Vaesen, Clapham.
Middlesbrough: Schwarzer, Reiziger, Ehiogu, Southgate, Queudrue, Morrison (Bates 89), Parlour, Boateng, Downing, Hasselbaink (Maccarone 74), Viduka (Job 78).
Subs Not Used: Doriva, Jones.
Goals: Viduka 14, 45, Queudrue 71.
Ref: P Dowd (Staffordshire).