June 24, 2009
Number estimated at two times more than 20 years ago
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A Baylor University researcher who has studied the Eastern Screech Owl for more than 40 years says an increase in the number of the owls that are red - known as "rufus" - is another sign of global warming.
The owls can be either gray or rufus, and Dr. Fred Gehlbach, research professor of biology at Baylor, says he has observed the rufus phase of the species increasing over the years. In central Texas, where Gehlbach conducts much of his research, he noticed a dramatic increase in rufus owls after the 1984 record cold winter. He believes as global warming continues, rufus birds will only become more prevalent.
He estimates 20 years ago, rufus owls made up about seven percent of the total population. Now it is closer to 15 percent.
"While gray is still the predominate color of the Eastern Screech Owl, I am seeing more and more rufus owls in places where they are common," Gehlbach said. "I'm not surprised by it. In fact, it makes sense. They do not have high survival rates where it is cold. As temperatures rise, so does the survival rate."
The color of the birds is genetically determined. The rufus-phase Eastern Screech Owl is mainly found in hot and humid places in the southern U.S. Gehlbach said its feathers are more porous and adequately dissipate body heat. The feathers of the gray owls are stouter and can protect against colder weather. In low light areas, rufus also is harder to see, decreasing chances a predator will find them. Rufus owls are predominately found in rainy cloudy places.
Gehlbach also said he has observed the owls nesting, or breeding, earlier than before. In central Texas, he has observed them nesting about a day earlier every three years.
Gehlbach has more than 150 peer-reviewed publications, faunal monographs and book chapters. He has written three books on the natural history of the U.S.-Mexican Borderlands, the lifestyles of suburban and rural Eastern Screech Owls, and the natural and unnatural history of suburban central Texas.
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