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NATURE HAPPENINGS - SEPTEMBER 2001

Marvels of Migration Part II - The Trip Home
by Damian Fagan

September is the season of return - excluding, of course, the after-Christmas return season. Students return to school. My family tax refund returns to me (in theory). But more spectacular, thousands of birds wing their way southward, returning to their wintering grounds and, perhaps, what we might call home.

Consider this. A tiny four-ounce rufous hummingbird, whose name is longer than its body, whirrs its way northward in spring to its breeding grounds in the lowlands and mountains of the Pacific Northwest. By July, the males have already arrived in Moab on the southward migration. His four months on the breeding ground in the Pacific Northwest, British Columbia or southern tip of Alaska does not make the rufous a resident. Nor will he ever see a family tax refund. He will probably have sired several generations of little rufous’s and split the country before I ever see a tax refund - whatever a “tax refund” is. No, the rufous and many of his neotropical migratory counterparts spend more time on their wintering grounds south of the U.S. /Mexico border than here in the U.S.; the ink is barely dry on their visas before they head home.

As the month progresses, we see other species of birds moving southward. Swirling pods of vultures or red-tailed hawks form great kettles, something Edwin Way Teale once described as “like a man walking slowly down the steps of a rapidly rising escalator.” The birds are in constant motion, wings held aloft as they soar upwards on warm thermals.

These and other raptors rely upon the winds to help them cover hundreds of miles in a day with little effort expanded on their part. Take a moment and sit on the edge of Bull Canyon in the La Sals or Gold Knob and watch the skies. Though you may not see hundreds of migrant raptors passing your point, you will see determined kestrels, soaring sharpies or gliding redtails heading south.

Perhaps you’ll observe hundreds of swifts and swallows catching their dinner on the run as they too move southward. Long ago, observers thought that swallows hibernated in the mud or flew to the moon to avoid the long, cold winter season. Those early watchers were astute - at least they realized that the birds had left, gone somewhere else.

But it is not the cold that these birds are avoiding. Rather, it is the shortage of food, insects primarily, that drive these birds to other places. If there were sufficient food resources available, perhaps that hummingbird would rather stick out the cold than undertake a perilous thousand-mile journey. That is why there are more insect eating migrants than there are seed eating migrants.

Though hummingbirds and robins migrate in the day, think of completing this task in the darkness, with daytime stopovers to rest and feed. Using the position of the stars, sun and moon, along with other sensations such as weak magnetic fields, odors, polarized light, barometric pressure and low frequency sound waves, these nighttime migrants pass overhead while we are deep in slumber. I often wonder how these birds react when they descend from the heavens to their self-appointed stop over location and that area is gone. Paved over or clear-cut or ravaged by a wildfire. Do they come to a crash landing, stand there stunned and perplexed or do they register the change and just move on? Certainly, the birds have had to make adjustments to Ice Ages and major catastrophic changes in their pasts, but today’s changes come much faster and seem to be of greater intensity. Just how these changes will affect the birds is anyone’s guess, but I’d have to say that the odds of getting a tax refund are better.

 
 
 
 

 

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