There isn’t a lot of information here about Storm-Petrels for a couple of reasons; first, there just aren’t that many reports or records from land, and second, you’d really need to get several miles offshore of Mayport to have a good chance of seeing them.
It seems like there is a natural event that pushes them close to shore or even up into the mouth of the St. Johns River about once a decade, but just for a couple of days. The last such event was in June 2012, where all three species of Storm-Petrels along with decent numbers of Great Shearwater could be seen from land – as far “up river” as the Mayport Ferry slips. These events usually coincide with a large amount of sargassum (sea weed) being pushed close to shore.
In any event, your best bets are looking from shore at Huguenot Memorial or Hanna Park, or even better – find a way to get on a boat and head out to sea. I used to take my Skiff 3-5 miles off shore fairly routinely throughout the year and have only once seen a Storm-Petrel during those excursions. My only other observations have been along the breaking waves at Huguenot.
Wilson’s Storm-Petrel Oceanites oceanicus
Wilson’s Storm-Petrels are most abundant offshore in mid-May to early June. They can also be seen throughout September with some effort (i.e., from a boat offshore). The highest known count of the species is twenty-five observed by Roger Clark on 18 July 1971. Mark Dolan observed one at the mouth of the St. Johns River following Hurricane Erin in early August 1995 (Rowan, 1995). Clark noted another fourteen on 16 May 2006 several miles offshore, aboard the Mayport Princess. I suppose these numbers make Wilson’s the statistically “most abundant”of the Storm-Petrels based on a very small sample size…which should work in my favor since it’s the only one of the three I haven’t personally seen here!
Leach’s Storm-Petrel Oceanodroma leucorhoa
Leach’s Storm-Petrel are best found in late May offshore of Duval County. One of the aforementioned “events” occurred from 22 to 24 May 2009 when multiple observers reported them in the surf at Huguenot Memorial Park. I observed two from my boat along the Mayport jetties on 22 June 2012, which is also the most recent county report.
Band-rumped Storm-Petrel Oceanodroma castro
Band-rumped Storm-Petrel are also most abundant in mid-May through June, with scattered reports in the fall. The earliest documented report is from one 102 miles east of Jacksonville on 1 May 1984 (Stevenson & Anderson, 1994). One was observed along with the Leach’s at Huguenot from 22 to 24 May 2009, and I saw six along a one mile stretch of river on 22 June 2012, the same day I recorded the two Leach’s noted above.