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Incredible journey of Swainson’s hawks

Photo courtesy University of Minnesota Swainson's hawk

Scattered palms and cecropia trees surrounded the pastures of the small farms on the coastal plain of western Panama. In places, traces of rainforest remained. A couple of toucans flew past, and the Caribbean sparkled a couple of miles to the north. It was mid-October and 75 degrees in the tropical morning, and the humidity was higher still.

It was not the place I expected to see familiar friends from home, but I should have. I had just left Medford a couple of days before, and the very last violet-green swallows and turkey vultures had departed. Oregon was preparing for winter.

However, in Panama, migration was in full swing. I found myself in the shadow of a swirling mass of several hundred Swainson’s hawks lifting off into the warming air for another day of travel in their month-long migration. Their destination was still 3,000 miles distant in the wheat country of northern Argentina.

A look around and I saw other kettles of Swainson’s hawks near and far rising into the humid air along with turkey vultures and broad-winged hawks. The numbers were impossible to estimate accurately, but it is safe to say there were many thousands of each. It was explained to me that this morning was nothing special. The guide described a day at the peak of migration when birds number in the hundreds of thousands. I had read about this event, but to see it made it real and truly impressive.

I imagined that a few of the Swainson’s hawks among the thousands were those I had seen raising young in the grasslands and sagebrush country east of the Oregon Cascades or in Butte Valley south of Klamath Falls.

Satellite tracking by scientists has begun to reveal their path south. Many Oregon birds head south into California and then over to Texas. After a pause to feed and put on a little more weight, they continue down the Gulf Coast of eastern Mexico and then cross back and forth across Central America avoiding the mountains. It is their path upon entering South America that is still uncertain. A look at a map reveals they must cross three mountain ranges comprising the Andes in northern Colombia. Each rises 8,000 to 12,000 feet in elevation. There is no avoiding this obstacle. They then pass largely unseen across the western Amazon Basin before reaching their wintering grounds in Argentina.

It is believed they do not feed between Texas and Argentina on a trip that lasts an estimated 25 days. While in Argentina they apparently feed largely on insects. There must be a lot of grasshoppers to make the 5,000-mile trip or longer worth the effort. The turkey vultures from the eastern United States and the broad-winged hawks that accompanied them are content to remain in northern South America.

It wasn’t that long ago that pesticides used in Argentina led to the deaths of large numbers of Swainson’s hawks and contributed at least in part to the steep decline of the species. The use of this pesticide has since been curtailed, and now in the last 20 years we have begun to see Swainson’s hawk numbers rebound.

As I pondered this incredible journey, I stood transfixed staring into the morning sky marveling at one of nature’s more impressive displays.

Stewart Janes is a retired biology professor at Southern Oregon University. He can be reached at janes@sou.edu.