The 25-year-old's contract with the Dons was due to expire this summer and he has now opted to join Birmingham on a two-year deal.
He leaves after 169 appearances for the Dons, who signed him from Wolverhampton Wanderers in 2009.
The Irishman becomes Birmingham's third signing of the summer, following the arrivals of Jonathan Grounds and Grant Hall.
Restore Data
| Team | P | W | D | L | F | A | GD | PTS | |
| 1 | Wrexham | 5 | 4 | 1 | 0 | 11 | 2 | 9 | 13 |
| 2 | Stockport CountyStockport | 4 | 3 | 1 | 0 | 8 | 1 | 7 | 10 |
| 3 | Barnsley | 5 | 3 | 1 | 1 | 10 | 6 | 4 | 10 |
| 4 | Birmingham CityBirmingham | 4 | 3 | 1 | 0 | 8 | 5 | 3 | 10 |
| 5 | Charlton AthleticCharlton | 5 | 3 | 1 | 1 | 5 | 3 | 2 | 10 |
| 6 | Lincoln CityLincoln | 4 | 3 | 0 | 1 | 9 | 5 | 4 | 9 |
| 7 | Huddersfield TownHuddersfield | 4 | 3 | 0 | 1 | 6 | 3 | 3 | 9 |
| 8 | Reading | 4 | 2 | 1 | 1 | 5 | 4 | 1 | 7 |
| 9 | Bristol Rovers | 5 | 2 | 1 | 2 | 4 | 4 | 0 | 7 |
| 10 | Exeter CityExeter | 4 | 2 | 0 | 2 | 5 | 4 | 1 | 6 |
| 11 | Peterborough UnitedPeterborough | 4 | 2 | 0 | 2 | 6 | 6 | 0 | 6 |
| 12 | Crawley TownCrawley | 4 | 2 | 0 | 2 | 3 | 5 | -2 | 6 |
| 13 | Northampton TownNorthampton | 4 | 1 | 2 | 1 | 4 | 4 | 0 | 5 |
| 14 | Mansfield TownMansfield | 4 | 1 | 2 | 1 | 7 | 9 | -2 | 5 |
| 15 | Rotherham UnitedRotherham | 5 | 1 | 2 | 2 | 3 | 5 | -2 | 5 |
| 16 | Wycombe WanderersWycombe | 4 | 1 | 1 | 2 | 8 | 8 | 0 | 4 |
| 17 | Stevenage | 4 | 1 | 1 | 2 | 2 | 3 | -1 | 4 |
| 18 | Bolton WanderersBolton | 4 | 1 | 1 | 2 | 2 | 5 | -3 | 4 |
| 19 | Burton Albion | 4 | 0 | 3 | 1 | 5 | 6 | -1 | 3 |
| 20 | Wigan AthleticWigan | 4 | 1 | 0 | 3 | 2 | 5 | -3 | 3 |
| 21 | Shrewsbury TownShrewsbury | 5 | 1 | 0 | 4 | 4 | 9 | -5 | 3 |
| 22 | Blackpool | 4 | 0 | 2 | 2 | 7 | 11 | -4 | 2 |
| 23 | Cambridge UnitedCambridge | 4 | 0 | 1 | 3 | 4 | 9 | -5 | 1 |
| 24 | Leyton Orient | 4 | 0 | 0 | 4 | 2 | 8 | -6 | 0 |
| > League One Full Table | |||||||||
