Birmingham have now failed to win any of their last five games and the shell-shocked team are suffering a dramatic loss of confidence.
The storm clouds are now heavy over St. Andrew's and this was their worst performance of the season.
On the other hand, Norwich City's new boss, Peter Grant, enjoyed his baptism of fire as the Canaries recorded their first away win in six months.
He had to be delighted with Jason Shackell notching the 66th-minute winner - his first ever goal for Norwich. He made a hopeful jump to make connection with a Darren Huckerby free-kick and the ball struck him on the back of the head and trickled into the net.
It was a body blow for a desperate Birmingham outfit who continued to struggle despite a powerful performance from David Dunn.
As usual, the Blues made a hectic start in an attempt to over-run the opposition, but the Canaries were more than alive to the situation and had little difficulty repulsing the home attack.
Birmingham's eagerness to impress was very nearly their downfall in the opening five minutes as their defence was sliced open by Robert Earnshaw and Carl Robinson to create a clear opportunity for Dickson Etuhu.
Fortunately for Birmingham Maik Taylor produced an excellent diving save to his right to keep the scores level.
But it was a ragged display from a Birmingham side which again had changes in defence. Their composure was easily rattled and they struggled to find any kind of rhythm.
They made elementary mistakes and Norwich were able to take advantage of this miserable situation to attack almost at will in the first period.
With Huckerby playing deep Norwich mounted several promising attacks, with the pace of Earnshaw causing particular problems.
Birmingham's current plight was highlighted midway through the first half when DJ Campbell, highly-rated by Bruce, fluffed a reasonable chance after Gary McSheffrey had made all the running to pull the ball back to the striker.
Paul Gallacher earned his keep with a fine save to keep out a Radhi Jaidi header but Norwich remained the more dangerous as indicated by the way the skilful Huckerby was able to open up the opposition.
The much-travelled striker made a solo break and finished with a low shot which required the international quality of Taylor to keep his goal intact.
Taylor continued to distinguish himself as he three times denied Earnshaw and also kept out another effort from Etuhu as Norwich exposed the frailty of Birmingham's defence, which was particularly suspect down the middle where Bruno N'Gotty and Jaidi continue to have problems adjusting to life in the Championship.
With Robinson and Huckerby creating chances for Earnshaw and Lee Croft, the Canaries had more clear cut openings and it was no surprise when they finally broke the deadlock.
Huckerby's free-kick from the left avoided Birmingham's big defenders and the jumping Shackell scored when the ball bounced off the back of his head.