September 4, 2020
A MORNING WITH SWAINSON’S HAWKS
By Barry Lyon
Our latest VENT Webinar, Raptor Identification 101, was presented yesterday, September 3, by my colleague Erik Bruhnke. Erik’s delightful “tour” of North American birds of prey was engaging and clearly delivered, complete with high quality photographs. When Erik discussed the Swainson’s Hawk, an elegant bird of the western and central part of the continent, I was transported back in time, more than 25 years, to an autumn morning I spent with Victor Emanuel on a bluff above the Rio Grande in South Texas, where we experienced one of the most memorable encounters I’ve had with any bird.
September and October are prime months for hawk migration, a time when millions of buteos, accipiters, kites, eagles, and falcons move south across the continent, bound for warmer climes and greater food availability. Of the almost two dozen species of raptors that undertake this annual fall phenomenon, one species that is especially prominent here in Texas at this season is Swainson’s Hawk. One of our most handsome birds of prey, Swainson’s is a large, long-winged buteo that occurs in the U.S. and Canada from March into October. It is an open country species typically associated with native prairie and high desert habitats, although it does well in certain agricultural settings. Every year in September and October, this species passes through Texas by the thousands. Because hawks prefer not to migrate over water, Texas acts as a natural funnel, with most of the continent’s Swainson’s Hawks pouring through this funnel as the birds make their way south toward their ultimate destination: the native grasslands of central Argentina, where they will spend the northern winter.
Near the end of a trip to the Rio Grande Valley, Victor and I made a trip to the Santa Margarita Ranch, located near the town of Zapata, below famous Falcon Dam. The ranch is legendary among birders for its wild ambience and for the long list of rare birds seen here. We have always loved this location. From atop the bluffs overlooking the river’s north bank, one enjoys unobstructed views of the forest-lined river for miles upstream and downstream and the Mexican countryside directly across. Arriving at sunrise, we understood that it would be a good morning to observe migration, as small landbirds seemed to be everywhere. In particular, we were in awe of the sheer numbers of Blue-gray Gnatcatchers streaming by and in the vegetation around us. Throughout the morning, we witnessed literally thousands of these little sprites moving past at eye level, apparently using the river as a corridor on their way south.
By mid-morning, as the day warmed, hawks began to appear. Swainson’s Hawks. First in ones and twos, the numbers quickly increased to dozens, then hundreds, then thousands—all streaming past and overhead. Occasionally, the hawks stopped to kettle in their dozens, but most simply passed by in a procession that lasted for two hours. From our elevated perches, we were able to study the birds at eye level, noting in detail the beautiful two-toned wings and diagnostic “bib” of the light morph birds, as well as more subtle identification marks. How fortunate we were to have been at that special location to witness such a fine spectacle. It was an experience Victor and I will never forget. Even after all of these years, when the autumn rolls around, we still talk about that glorious morning on the river.
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