Hard to pass up a question like this because it's probably unanswerable.
Anyway, here are a couple of quotes from Handbook of the Birds of the World
(del Hoyo et al., eds.), vol. I, pp. 264, 267:

"...some species [of storm-petrels], such as Wilson's Storm-Petrel, are
said to be amongst the most numerous of all birds.... [Wilson's
Storm-Petrel is] traditionally considered one of the most abundant of all
seabirds...."

Hal Opperman

>Help! Anybody out there have the answer to this one?
>
>Gene Hunn.
>
>
>>Date: Tue, 21 Oct 1997 16:49:38 -0700
>>To: "Wendy Johnson" <WJohnson at evansgroup.com>
>>From: Hal Opperman <halop at accessone.com>
>>Subject: Re: Media FYI
>>Cc: hunnhome at accessone.com
>>
>>At 11:41 AM -0600 21/10/1997, Wendy Johnson wrote:
>>
>>>Hal,
>>>
>>>Could you or another SAS board member confirm this?
>>>
>>>BIRD POPULATIONS - NATIONAL GEOGRAPHIC. I'm a researcher at National
>>>Geographic trying to determine what is the most abundant bird in the
>>>world. We list the Wilson's storm petrel as the most abundant. Does anyone
>>>have a good reference? >>> Jeanette Howard Email: jhoward at ngs.org Phone:
>>>202-857-7232
>>
>>Wendy:
>>
>>I've heard that expressed as fact before, but can't affirm it without quite
>>a bit of research. I'm forwarding your mail to Gene Hunn who can probably
>>get you on track to a more definitive answer faster than I can.
>>
>>Hal
>>
>>
>>***************************************************************
>>Hal Opperman - P. O. Box 286 - Medina, Washington 98039 - USA
>>halop at accessone.com - phone (425) 635-0503 - fax (425) 635-0271
>>***************************************************************
>>
>>
>>
>>