Thursday, November 24, 2016

Birds of the Quarry, 5 - The Gulls

Gulls must be the most neighborly of creatures at Halibut Point. They don't mind your civilized presence, at a certain remove. They never take their eyes off you, but they rarely scold either. They never try to hide. If you get too close they lift off into the air.

Gulls come to Halibut Point for some of the same reasons I do, stepping away from crowds and cares to straighten out their feathers. They animate the quarry where the stillness might otherwise seem ghostly. They have an aboriginal presence when I walk unannounced into their busyness.

At the quarry they gather amicably for a fresh-water bath without squabbling over scraps. Generally they stick to the center to minimize intrusion.

The confabs of Herring gulls and Great black-backed gulls sometimes include Ring-billed gulls.

Sooner or later they get on to preening and drying chores on a nearby  ledge, or circle up and out to prospects at sea.

The masters of flight decelerate with tail and body arched, wings articulated for split-second adjustments, primary feathers opened on the up-stroke to lessen drag and maintain lift. They maneuver as smoothly as we reach for a doorknob.

They pull themselves through the air by reaching forward with their wings, not by pushing them to the rear. Wingtips bend and rotate to the task of propulsion. The wings scull in figure-eights to contribute forward momentum. Counter-intuitively, to our logic, the power stroke ends with the wing swept far forward.*


Rising off the water is hard work for heavy duck-like birds that taxi on their feet and flap vigorously.  Birds favored to soar, like gulls, achieve lift by simply extending their cambered wings in a light wind. Air flowing faster over the upper surface than below it pulls the bird upward passively. Similar pressure differentials make a spinning baseball curve and are mimicked in aircraft design.

Adaptations in the gull's  honeycombed skeleton, its feathers and its diet give it advantages for inhabiting all the continents and oceans of the earth. Modern anatomical research illuminates these facts without reducing the wonder of their coordination into a particular life. That wonder can be freshened with every ramble at Halibut Point. 

* See "Flight" in Chris Leahy's The Birdwatcher's Companion.

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