Saturday, September 20, 2014

Swift Watch

September wouldn't be complete without  Swift Watch, when thousands of Portlanders come to watch thousands of Vaux's swifts come to roost for the evening in a chimney at the Chapman Elementary School.  There were about 4,500 swifts on the night we watched them, and they were amazing.  As sunset approaches, they begin to swoop and circle, and eventually form tornadoes of birds that spiral into the chimney in waves.  The noise from the birds and the noise from the crowd is intense.  They make their way from as far away as Alaska and Yukon to Central Mexico and Costa Rica, where the flying insects that they eat are plentiful in the winter. The week before we went to Swift Watch, we saw a talk at the Audubon Society given by Larry Schwitters, who has been studying swifts in Washington and throughout the Pacific Northwest.  He spent four years surveying waterfalls, looking for black swifts which actually nest behind them.  Now he is studying Vaux's swifts and learning some surprising things about them.  

One of the things he is doing is looking for likely spots where they may roost. He ferrets out old, brick chimneys, and if they are a proper diameter (neither too small for them to fit inside comfortably, nor too wide so that owls can get in at night and feast) he tries to determine if they can be observed entering at dusk or leaving at dawn during fall or spring migration.  Swifts also have been known to roost on the exterior of brick structures and on the bark of trees, but hollow snags and chimneys have many advantages.  He has taken temperature measurements and determined that the bricks themselves do more than just provide something for their feet to grip, they actually retain heat and help the birds to stay warm at night.  There are so many suitable brick chimneys along the east coast that swifts have apparently stopped nesting in snags altogether, but along the west coast chimneys are more scarce. This scarcity can lead to huge numbers of swifts using the same chimney, a truly spectacular sight.  The one big disadvantage of these artificial structures is that they often have wide ledges at the top, where enterprising predators can perch.  Predators will go there in the mornings, with all the swifts trapped inside, and simply wait for them to come out to pick them off one by one.  To protect them, thin, vertical metal barriers can be placed around the chimney opening.

In addition to the Chapman school in Portland, he mentioned that there are perhaps 900 Vaux's swifts roosting in the chimney of the St. Johns Cinema, which can also be seen entering around sunset and leaving around sunrise.  The Chapman School apparently is not at all thrilled that thousands of people descend on their school grounds every September evening, and definitely refuse to welcome them at dawn and in the springtime when the swifts are roosting there once again during spring migration. But looking at the huge crowds this phenomena attracts, I can't help but think that if Chapman School hasn't been able to take advantage of this to help fund all sorts of programs at their school,  something is definitely wrong. And the fact that thousands of people gather each evening to watch birds together means something is surely right about Portland!

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