Friday, April 27, 2012

Northern Gannet at SEFI - Evidence of Climate Change?

The Farallon Islands are known for attracting rare and unusual vagrants. These have included songbirds more common to the east coast that have migrated up the wrong coast and birds from Asia that ended up on the wrong side of the Pacific. But this week we had an exceptionally rare visitor to the island.
Northern Gannet crossing in front of Saddle Rock (photo copyright Sophie Webb)
This Northern Gannet was first spotted in Fisherman's Bay on April 25th while we were doing our daily Pigeon Guillemot census. This represents not only the first island record and first California record for this species, it is actually the first known record for the entire Pacific Ocean. An exceedingly rare sighting.

Northern Gannet crossing Mirounga Bay (photo copyright Sophie Webb)

Having seen gannets on several occasions on the East Coast, I instantly recognized it, but then realized that I shouldn't be seeing a gannet here and tried to turn it into something more likely. Maybe a Masked or Red-footed Booby. Both are superficially similar and have been spotted here before, though also extremely rare for California. But a quick glance at the field guide confirmed the original identification. It must be a Gannet, there is nothing else it could be.

Northern Gannet close up (photo copyright Sophie Webb)
There are three species of Gannet in the world. The Cape Gannet, the Australasian Gannet and the Northern Gannet. The Cape Gannet only occurs around southern Africa, while the Australasian Gannet is found in the temperate seas around southern Australia and New Zealand. The Northern Gannet is typically only found in the north Atlantic Ocean. So all three species seemed equally unlikely. At least the Australasian Gannet would be the right ocean. But both the Cape and the Australasian species have dark secondaries and black on the tail, which this clearly did not. So Northern Gannet it is.

Northern Gannet (photo copyright Sophie Webb)

But what is it doing at the Farallones? As you can see from the range map below, it has no business being here. How did it get to the Farallones?
Northern Gannet range map
The likely answer is that it came across through the now open water of the Northwest Passage. Climate warming has resulted in a reduction in pack ice and and an increase in open water all the way across the top of the continent.  This bird probably followed that water and ended up in the wrong ocean. In fact, just last summer, there were two individual Northern Gannets reported in the Arctic Ocean north of Alaska.  That was a first for that region and a clear sign that a warming planet is opening up new avenues for seabird dispersal. Maybe this is another case like the one in the Arctic or maybe it is even the same bird, having migrated down the West Coast for the winter and finally stopping for a rest in a sheltered cove near our little island. We can't know for sure, but we do know that a warming planet and more open water will allow for more mixing of marine species between the Atlantic and the Pacific. Maybe someday we will be seeing Atlantic Puffins and Razorbills at the Farallones and Tufted Puffins and Cassin's Auklets will be breeding in Newfoundland.


biobabbler said...
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Kathleen Jacques said...

Great photographs Sophie! And congratulations on having the camera ready. I live on a lake in Upstate NY in a migratory freeway; more and more I am seeing surprise travelers, but your observation is both surprising and alarming.

Jacoba Charles said...

Hi there,

I'm writing an article about the Farallones gannet for the Point Reyes Light, and I would like to quote this blog post--can anyone tell me who the author is, and what their title is?

Thank you.

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