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California least tern

Many (but not all) species of birds pack up and leave one part of the hemisphere and fly thousands of miles to arrive at another.  Upper Newport Bay, one of the few remaining protected wetlands on the California coast, hosts thousands of migrants from the north during the winter months.  Seeking warmer weather, protected habitat, and abundant food, shore birds, water fowl, and smaller birds like warblers and sparrows join us here at the bay.  On the mud flats, look for the long-billed curlew with its extraordinary down-curved bill, or check the water close to shore for beautifully colored ducks like the American wigeon or the cinnamon teal.  In the uplands, you might see or hear a favorite winter visitor:  the white-crowned sparrow.

Scientists are not certain about what sparks migration or how exactly birds know where to go.  Shorter days in the fall or perhaps some genetic mechanism may send birds from Alaska, Canada, and the Northwest US down the Pacific Flyway, as the north-south corridor on the west coast is known.  The position of the sun, the earth’s magnetic field, and visual cues may guide their paths, though tall buildings and artificial light can interrupt their progress.  However they do it, birds have incredible navigation systems that enable them to follow the same routes from year to year with great accuracy.  Some fly for days at a time, while others are sprinters.  Flying times last between 25 and 250 miles per day.  In the spring, when one set of migrants returns north to nest, another group takes its place, flying up from Mexico and the tropics to nest in protected areas here at the bay.  From Vista Point, look for the endangered least tern (pictured above) settling into the sands of Tern Island in April!

Resources:

The Cornell Lab.  “The Basics of Bird Migration:  How, Why, and Where.”  January 2007.

https://www.allaboutbirds.org/news/the-basics-how-why-and-where-of-bird-migration/

Check out the animated migration map on this site to see migration patterns for the Common Yellowthroat.  You’ll see that this colorful little bird is a permanent resident in our area.

Peter Berthold.  Bird Migration.  A General Survey. Trans. Hans-Günther Bauer and Valerie Westhead. 2nd ed.  Oxford University Press, 2001.

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