Wednesday, October 14, 2009

Vaux's Swifts

Swifts! What a fascinating bird they are. They take flight at dawn and remain aloft until sunset. They cannot perch. They fly faster than any other bird in a straight, powered flight at a top speed of 105mph. They may fly 500 miles from their nest before returning. From a distance they appear to be swallows to the untrained eye, but are vastly different. They fly higher, faster, at greater distances and their closest relative is the hummingbird. Close up they may look like a Batman version of a bird. Their eyes are large and sunken, protected by a baffle of feathers to the fore, to protect their eyes against being hit by the insects they eat. At night they gather together and cling to vertical surfaces like bats do on cave ceilings.

There are two types of swifts that visit our area, the pacific northwest; the Black Swift and the Vaux's Swift. The Black Swift nests and roosts behind waterfalls, and the Vaux's Swift nests and roosts in upright hollow snags and chimneys. In both these cases the conditions must be just right.

The Black Swift may best describe why these environments are musts for nesting and roosting. The Black Swift is rather rare in our area. A nest has never been found in Washington. What is needed is a waterfall that provides room behind the waterfall, for obvious reasons, a surface that provides enough grip or voids the be able to cling for both birds and nests. The waterfall should face west to catch the sun at sunset. The reason for this is that the adults are on the wing all day catching insects. During this time the young is receiving no food. The waterfall provides the coolness to put the young into torpor, a half-hibernation state. The late sun brings them out of this state to feed when the adults return from the days feeding. Their nests are made of moss and mud, and unlike the Vaux's, there may be several nests to a waterfall.

The Vaux's Swift, on the other hand, may have a gathering of 21,000 birds in a chimney at a time, but there is only ever one nest per chimney. Frank Wagner Elementary School in Monroe, Wa, the place where I was introduced to the swifts this year had around 12,000 birds at it peak. When I got there they had dwindled down to around 2000 birds a night. Sumas Old Custom House is another great spot to watch them. To satisfy the roosting habits of the Vaux's the chimney needs to have a rough surface, (or seams), such as old brick. It needs to not be in use as an active chimney. It cannot have an opening at the bottom such as the tulip chimney in Mt Vernon, but only an entrance at the top.

The gathering begins about an hour before sunset. You begin seeing them at height, few in number at first, then more and more. You will see them start to swirl in a large cloud of birds, then disperse, and swirl again. The closer to sunset you get the larger in number they become, and more and more birds will make practice dives at the chimney, none going in. Again, they will gather, go into a great swirling cloud and suddenly disperse. Suddenly they will be nowhere in sight, and again, they will be. Perhaps 15-20 minutes before sunset on or two will drop into the chimney. At sunset they will make a great swirl like a black dust-devil and the first group will drop in. Ten minutes after sunset the greatest grouping will swirl into what looks like a black tornado, like something out of the Wizard of Oz, and it will look like they are being vacuumed into the void. A truly amazing sight!! Twenty minutes after sunset and the last few stragglers will finally flutter down into the roost.

Inside they cling to the walls and the backs of others, like a great thick build-up of soot. And there they stay until sometime around dawn where they climb back up the walls, and not having the ability to perch, they drop off the edge of the lip, catch the air in their wings, and off they go for a full days flight.

How cool is that?

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