Delhi '08 has more girls than boys

An article in Indian Express today reported a turnaround in the low female to male ratio in Delhi.

In 2001, the sex ratio was 905 :  1000 [based on the 2001 Census]

In 2007, the sex ratio at birth was 848 : 1000 [cited in this article]

In 2008, the sex ratio at birth was 1004 : 1000 [based on births reported by Chief Registrar - Births and Deaths, Delhi]

How credible are these numbers? What accounts for this turnaround? Expect to hear discussions and arguments around these questions over the next few days in the media.