Sunday, April 8, 2012

Migration begins

    It is early April.  Long streaming days of cold, wet and depressing weather have sent us fleeing  north for spring break to the area around Sequim.  Here there is a rain shadow from the Olympic mountains and here, too, we might find surcease from this hideous spring. And so it has proved.
Striped Peak

    We are sitting at Salt Creek  campground along the Strait of Juan de Fuca, where we stopped for a bathroom break.  The heavy rain & slashing winds of the night before have broken open, and we have been enjoying some strong spring sunshine.  Sitting  east of us in the near distance is Striped Peak,  one of the last foothills of the Olympic Mountains before the cold waters of the Strait devour its base.   I was sitting in the car, idly glancing around, when I saw a couple of Bald Eagles soaring over the peak.  There was a mad scramble for binoculars (both pairs!)  and then jostling for the  best viewing place.  Binos glued to our faces, we called out sightings and descriptions back and forth: “No, look, look, to the left of the peak, see that scraggy tree, just above it.  Ooooooh look, there’s another one!”  As we watched, a thermal updraft formed, and  migrating hawks raced to catch it.  This is spring hawk migration along the Strait.  For me, it took me back 22 years to Cape Flattery and other April raptor migrations I have watched.

          Here in western Washington state, the birds of prey are making their migration move north.  It is the Red-tailed Hawks, the Bald Eagles (and occasional Golden Eagles),  the falcons,  the accipiters like Sharp-shinned and Coopers Hawks, and others that leave their winter territories in the southern lands and follow the Pacific coast line north.  Some stop in Washington state, and set up breeding territory,  but many more push through to Canada and into Alaska to find their place, their mate and rear this year’s young.  

Crossing the cold water to Vancouver island
     A big challenge for these birds is the Strait of Juan de Fuca.  A frigid body of salt water, it forms the northern border of Washington state, sharing its waters with Canada.  They have to cross it to get north.  It can be as much as 15 miles across to Vancouver island, and it takes strong flight muscles to get a bird across without getting pulled down into 40 degree water.  Falcons can do it:  I’ve seen both Peregrine and Merlins get a fine head of steam and just power themselves across on the strength of those oar-like wings.  But surprisingly, most of the other common travelers are fairly weak flyers over long expanses of cold water.  They need to find another way. 

A Red-tailed hawk, wings set to ride the thermal
     The strategy they use is to ride the “thermal elevator”.  Thermals are updrafts of warm air that rise from the ground and can go many thousands of feet into the air.  Thermals form a spiral, rising column of air; the hawks and eagles somehow feel out these currents.  They set their wings to glide and allow the warm air to lift them to great heights.  Along the Strait of Juan de Fuca, they get to a certain height, then set their wings to glide north.  They then simply slide across the next fifteen miles, gradually losing elevation and arriving on Vancouver island, ready to rest and feed and prepare for the next leg of the journey.

     I first learned about all this from Bud Anderson, falcon biologist and educator extraordinaire, who discovered this Strait of Juan de Fuca spring migration phenomenon  further west near Neah Bay, at Cape Flattery.  It was with Bud and his Falcon Research Group volunteers that I spent several early Aprils, on a low mountain near Neah Bay, watching the hawks, falcons and eagles head north.  After the research project ended, I really missed seeing the migration.  So what happened for us this week was a real treat.

    What we saw at Salt Creek  was several factors that came together to make the thermal elevators possible.  For example, the hot spring sun had been warming up Striped Peak, but unevenly: one warm side of the hill with one cold side sets up the spiraling updrafts.  In addition the peak sits right on the cold water of the Strait, which adds its own complexity to the thermal recipe.  There was a weak southeast wind;  from my years at Neah Bay I remembered that east winds along the Strait really aid in the formation of thermals.   In addition, Striped Peak is near the narrowest point of crossing to Vancouver island - about 10 miles. If I’m a hawk and the day’s conditions are questionable, I’m going to pick the shortest crossing.

Look closely:  hawks soaring above the trees
     As we watched these raptors over Striped Peak, we noticed others coming to join them.  I remember Bud teaching us that all of these spring migrants are hot to trot, ready to cross the water and get down to business.   So they sit in trees near the Strait, waiting for good conditions and also watching each other to see if another migrant has found a great thermal elevator.  If it looks promising, they race to join it.  Thermals are very ephemeral, and the birds have to move fast to get on the elevator.  Today we were seeing that same thing;  a small group of two or three quickly became  six, then nine.  These groups of circling hawks are called “kettles”, which refers to the way they look like they are circling in a soup pot.

       Not all thermals have enough lift to get the birds high enough to cross.  Today we watched the birds in the kettle shift and adjust, trying to find the best spots.  The thermals did not seem to generate enough lift for most of the birds, although Glen was certain he saw one bird gliding over the Strait.  By about 2:30 clouds were covering the sun and the thermal elevators shut down for the day.   The birds dispersed and disappeared. 
Sunset along the Strait
      We headed back to our snug berth along the Dungeness Spit.  The heavy clouds turned to rain and then broke briefly for a beautiful sunset.  I thought about the hawks, now settled down in a tree somewhere along the water’s edge.  Hopefully they found a fish, a vole, a small bird to eat before the cold night ahead.  They will wait for morning, for better conditions, to try again.    

     I fall asleep and dream of them, wheeling, rising and turning, disappearing into the mist, making safe passage north to home...


•  Falcon Research Group:
•  Red tailed Hawk Photo by Ellen Wilson.  See her blog at:
•  All other photos by Glen Buschmann

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