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Sunday, August 19, 2012

Endless summer

It's been breezy and foggy for the past two days, with 15-25 knot winds out of the northwest.  Looking out to sea yesterday afternoon, there was a steady stream of phalaropes heading north.

Phalaropes always look so small in rough sea conditions. 

I looked again today, and noticed more phalaropes and good numbers of Sooty Shearwaters (Puffinus griseus) a little further offshore.  There were at least 5-10 shearwaters passing by every minute (viewed through a spotting scope).

These are distant views, but this seascape shows these seabirds in their element.  [Click on the photo for a larger version.]  Look for the long, narrow wings held stiffly out to the sides.  In light winds, Sooty Shearwaters fly with a series of quick wingbeats interspersed with glides.  In stronger winds they fly in steep arcs, wheeling up and down with little flapping (description from Howell 2012). 

Researchers have used electronic tags to discover Sooty Shearwater migration routes.  Here's what they found:

Shearwater migrations originating from breeding colonies in New Zealand. 

(a) Interpolated geolocation tracks of 19 sooty shearwaters during breeding (light blue) and subsequent migration pathways (yellow, start of migration and northward transit; orange, wintering grounds and southward transit). The 30° parallels, equator, and international dateline are indicted by dashed lines. 

Shaffer S.A. et al.  2006.  Migratory shearwaters integrate oceanic resources across the Pacific Ocean in an endless summer.  PNAS 103: 12799-12802.

Sooty Shearwaters are using the entire Pacific Ocean basin.  An individual bird might cover ~65,000 km (39,000 miles) in one year!  

They breed in the Southern Hemisphere near New Zealand, Australia, or Chile (during the austral summer).  Then they migrate to the Northern Hemisphere and spend the non-breeding season off Japan, Alaska, or California (during the boreal summer).  Scientists have remarked that because Sooty Shearwaters migrate between two summer seasons, they essentially live in an "endless summer."

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