I got bored, so I did some calculations. Sorry about the formatting, it's just impossible to make it perfect.
Month______Total_______Average per day
January_____120________3.870967742
February____101________3.482758621
March______133________4.290322581
April_______131________4.366666667
May________132________4.258064516
June_______137________4.566666667
July________124________4
August______138_______4.451612903
September__120________4
October_____144_______4.64516129
November___133_______4.433333333
December___141_______4.548387097
Total number of birthdays: 1554
Most birthdays: 11 on both April 2nd and November 14th.