In June, messages like this one began pinging around on the bird lists:
“There is increasing evidence of a die-off of Great Shearwaters along the Atlantic Coast of the Bahamas. Most of the information comes from Abaco where there is a long coastline and several active birders. I would be interested in learning if other locations in the Eastern Caribbean and southeastern US are experiencing similar die-offs.The shearwater die-off is a phenomenon that happens every five to ten years. In the Bahamas it lasy occurred in 2007. According to the late Dave Lee these are young Great Shearwaters migrating from their natal home in the South Atlantic to their feeding grounds off the US and Canada, The combination of poor food supply and wind conditions in the doldrums that make the passage unusually strenuous leads to the birds expending all their energy and expiring. It is a normal event for this species and has been recorded many times.” –Tony White
Indeed, it is normal, but as you can see from this note, it is not consistent in magnitude from year to year. On SEANET beaches, we start seeing Great Shearwaters on our southern beaches in June, and by July, Seanetters are finding them all the way up through Massachusetts. Though the birds turn up every year, their numbers vary. This summer does appear to be a bigger year, though not by much based on our data alone. Last summer, we had a total of seven carcasses across all beaches. As of today, we’ve had ten reported, though numbers of GRSH always taper off by the end of July, so I don’t expect to see many more. In 2013, we had only three GRSH turn up. Which of these is “normal?” I don’t know.
I was honored to contribute a bit to a paper on the subject that mentions all the complicating factors–are we just looking harder now than we used to? Possibly, though at least over the past few years, SEANET data has been consistent. We will have to see if any long term trends emerge over the next ten years of Seanetting, but right now, it looks like shearwaters have good years and bad years, mainly hinging on the weather. There are always the marginal individuals that, in a good year, may eke out a living, and in a bad year not.