Why didn't Fawkes turn up??

[scamjunk22]

No: HPFGUIDX 143293

Thanks for the response on my previous doubt about Harry's blood.  Here's another of my doubts....

When the duel between AD and LV was taking place, Fawkes comes there 
and swallows an avada kedavra aimed at AD... without which AD would 
not be alive... and the ministry is SO very far away from Hogwarts.

So, when the entire conversation between AD and Draco (DM) was taking 
place on the castle ramparts itself (IMO, ample time for Fawkes to have 
sensed danger to its master), why didn't Fawkes turn up?  It would 
have been obvious that Fawkes would have turned up immediately, yet 
he does not 'appear' to be there until after everyone's gone inside. 
Why has this important link between AD and Fawkes been ignored, in HBP 
all of a sudden??? 

be safe,
scam.