An examination of the histogram shows significant seasonal variations. The months July - October show higher than expected births and March - May show the most significant decline in births. Perhaps the most reasonable explanation is that conceptions are up in the months of October through January and down in June through August. You be the judge.

The implications for the original questions are that slightly fewer persons are needed to get a single match and slightly more persons are needed to have every day covered if the distribution is not uniform.