ShareThis3 April 2011
Something funny’s going on at sea this month.
Great Shearwaters are appearing in unprecedented numbers off the coast of Australia. How unusual is this? Well, it’s about as unusual as an 8.9 earthquake and tsunami. It’s never happened before.
Great Shearwater photographed off Portland (Australia) this week. Photo by Peter Lansley.
This isn’t an uncommon seabird. There are estimated to be about 15 million adults in existence, though they only breed on a small number of sub-Antarctic islands (Tristan de Cunha and Falklands groups). Normally, they migrate north across the equator through the Atlantic ocean. With a global range of almost half the planet, it’s no surprise they turn up in dribs and drabs off Australia – though to date, there has only been three confirmed records.
So, 50 birds off Port MacDonnell and another 8 off Portland this week, adding to the three or four records already this year from Australia and New Zealand, is incredible. There was also another record just in from Ian May off St Helens.
Whole flocks of birds have moved, uncharacteristically, half way around the planet. The only reason seabirds do this is to find food and when you can glide with minimal effort over vast distances for six months of the year, there’s nothing stopping you except knowing where to look.
We’re in the heart of a La Nina weather event at the moment. This means that there is unusually-warm water off Australia and our local seabirds are suffering badly. In contrast, the coast of Peru is experiencing some of the richest sea conditions its had for a long time.
It’s possible that our Great Shearwaters have originated from the southeast Pacific as they’d normally be heading north at this time of year and not returning to breeding grounds until about October. Finding themselves in food-poor Australasia, it’s no surprise that flocks are appearing in the Bonney Upwelling. High densities of Blue Whales have been seen close to the coast this year, no doubt seeking out the best places to forage for krill.
How does a seabird that normally heads into the North Atlantic know to suddenly change its movements by 90 degrees and head west? It’s remarkable and eerie at the same time. Are we seeing a major change in global ocean conditions or just a freak anomaly?
That the entire global distribution of a bird can be affected by weather and sea condition events like this is staggering. It makes you wonder what will happen as our global ocean temperatures continue rise, creating a dearth of food available to birds like this. Maybe Great Shearwater will become seen with increasing occurrence off Australian shores.
I think a downwind west to east dispersal in a large low pressure weather system from South Africa/ western Indian Ocean is the most likely provenance, 100 degrees of longitude compared to 140 degrees upwind from SE Pacific.
Neil, thanks for your thoughts. Is this a system that you’d say is unusual this year? Why would we not have seen this event before, in your opinion? Great to hear from you : )
I crewed on the topsail schooner Enterprize a replica tall ship on a voyage form Portland to King Island and onto Melbourne and we observed the Great Shearwater invasion. They took some identifying but some photo’s and a close encounter proved beyond doubt what they were.
The vessel departed Portland at sunrise on the 2nd of April 2011. The weather was partially overcast with sunny patches a light south westerly breeze increased throughout the day. The vessel headed in a southerly direction towards the continental shelf at around 6 knots under motor to catch a good following breeze for Cape Wickam, King Island.
Great Shearwaters began to be sighted as we approached abeam of Laurence rocks. Throughout the day the day there were regular sightings of Great Shearwaters circling the boat flying alongside and occasionally landing on the water. I would estimated that one was viewed every 40-60 minutes. Back browed and shy albatross were also regularly sighted. During the mid afternoon there was a large congregation of both types of Albertross and dolphins possibly around a school of fish. At this time there were as many as 10 Great Shearwaters present.
The following day as we approached Cape Wickham Great Shearwaters were still present but in lesser numbers.
On April 3 while sailing from Sea Elephant bay to Apollo bay in Bass Strait there were also occasional sightings
Simon, I was not referring to a particular storm system but just an opinion that these birds have come East in a system from the SW Indian Ocean rather than West from the SE Pacific. It will be very interesting to see how this exciting event plays out and when it is written up a close look at preceding weather patterns may give us some clues. Good luck to those on the special Port Mac pelagic on 17th April.
Weird indeed they should be headed our way; here off the east coast of Canada. Too bad more of them could not be satelite tagged thus we might get some understanding what is going on, to the best of my knowledge few if any are tagged right now. Someone go out and tell them it is coming on summer here in the great white north.
[...] of other notably rare birds in the last two years including New Zealand Storm-Petrels and Great Shearwaters, maybe we should expect more to turn up. Perhaps it has something to do with the onset of another [...]