Memories of Snake River Birds of Prey NCA

American Yellow Warbler - Setophaga petechiaThe Morley Nelson Snake River Birds of Prey National Conservation Area has been set aside to promote the protection and preservation of raptors. These birds sometimes gather here in large numbers. The steep rocky cliffs lining the inner canyon that carries the Snake River through the wide plains of Southern Idaho are well suited for their nesting needs.

Southern Idaho has been forged in fire and ice. Ten to twelve million years ago the volcanic hot spot that today simmers under Yellowstone Park drifted through this valley. More accurate to stated, the continental crust drifted over the hot spot and left behind the wide plain we see today.

Ten thousand years ago there was a great inland lake we now call Lake Bonneville. Scientists believe an alluvial dam held the water in Utah, but as glacial ice melted it raised the lake to its highest levels, finally pushing through the soft alluvial berm at present day Red Rock Pass in Idaho. As the berm dam collapsed, it released a layer of water over 400 feet deep from the 32,000 square mile lake and produced a catastrophic flood that followed the Snake Basin, gouging the 600 foot deep inner canyon and carrying house sized boulders for hundreds of miles. The flood waters reached speeds of seventy MPH and passed 33,000,000 cubic feet of water per second at its peak. The peak flow lasted for weeks, but even after it subsided, the water continued flowing for years.

Today the Snake River Plain is a rich food source for predatory birds. Piute Ground Squirrels, known locally as “Whistle Pigs”, occur here in large numbers, and provide nourishment for highest concentration of nesting Prairie Falcons in North America. These birds comprise the largest contingent of the raptor population here. Up to 800 pairs of hawks, owls, eagles and falcons are known to nest in this area. The larger members of the raptor community have Black-Tailed Jackrabbits to fill their nutritional needs. Migrating raptors also rely on this region for refueling on their sometimes long journeys north or south.

I’ve not timed my visits here well enough to witness the great raptor spectacle I’ve heard about. January is the time to visit for the peak activity of the raptors. For this is when the squirrels bear their young and the raptors have their best opportunity to capture prey. But if you plan to exploit the opportunity to visit in this time frame, dress VERY warm. The mercury may be in the 20°F range when you get there.

My visits have been in late May and while the temperatures are pleasant, raptor numbers are low. I was able to meet a few Prairie Falcons zooming past at a distance, but when I followed the roads down into the canyon where the river flows at Swan Falls, I had some nice encounters with passerines and waterfowl. The gallery below gives you a glimpse of those meetings.

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