Friday, April 04, 2008

Hawk Migration

Audubon South Carolina’s Director of Bird Conservation, Jeff Mollenhauer, recently returned from a vacation to the Rio Grande Valley of Texas, an area that is well-known as a bird lover’s paradise. One can find a huge diversity of birds there because it is the convergence of temperate, tropic, and coastal zones.

Amidst all the flashy specialty birds such as Green Jays, Altamira Orioles, Aplomado Falcons, Gray Hawks, Greater Roadrunners, etc. was a phenomenon occurring that was so fascinating that it is hard to tear yourself away from…hawk migration! This is the time of year when Broad-winged Hawks are streaming through southern Texas as they return to their breeding grounds in the eastern U.S. and Canada. It is possible to see thousands fly by in a single day! Jeff spent three days observing the hawk migration in southern Texas and was lucky enough to see more than 1,000 migrating hawks.

Broad-winged Hawks migrate by catching “thermals” or rising currents of hot air where the sun is warming the earth’s surface. After soaring high into the sky, sometimes as high as 3,000 feet, the hawks will break from the thermal and begin to glide. As the hawks glide lower and lower, they will begin to search for a new thermal so that they can again rise high into the air. On a good day the hawks can travel more than 300 miles and rarely have to flap their wings. Broad-winged Hawks often form large groups or “kettles” when they find a good thermal. Some kettles can contain hundreds or even thousands of hawks! Check out the picture of kettle of Broad-winged Hawks (at right). How many do you count?

Since the Broad-winged Hawks are now streaming through southern Texas, we can expect to see our first migrants in South Carolina pretty soon. They typically begin to show up around mid-April in South Carolina, so keep an eye out for soaring hawks with a black-and-white striped tail. You may also locate them by listening for their call, a high pitch whistled “kee-eeee”.

Here in South Carolina, Broad-winged Hawk migration is broadly dispersed during spring migration and not as spectacular as fall migration. During fall migration a good spot to see hundreds of migrating hawks in South Carolina, or perhaps even a thousand on a really good day, is the Caesar’s Head State Park Hawk Watch and the peak is during mid-September. For a once in a lifetime experience head to Veracruz, Mexico in early October and you might see more than 100,000 migrating Broad-winged Hawks in a single day!

Images by Jeff Mollenhauer

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