Habitat Reduces Risk of Pheasants Freezing to Death
The major cause of pheasant winter mortality is not starvation, it is freezing. The pheasant’s physiological processes can produce only so much heat, and as temperatures drop, more and more body heat is lost to the surrounding air. At some temperature, called the “lower critical temperature,” more heat is lost than can be produced, and the bird freezes.
Pheasants will spend their winter nights roosting in grass cover or wetlands. The dead grass of roosting cover makes a nice insulated bed which protects birds from the wind. While the temperature near their beds may be 0°F, the 20 mph wind three feet above their heads produces a -39°F wind chill. To survive the 0°F in the grass, the pheasants must use 22.42 kcal of energy each hour. Without the grass cover, the pheasant needs 28.01 kcal each hour to survive the -39°F wind chill – meaning inadequate cover causes them to burn 25 percent more per hour. It’s difficult enough trying to survive a 16-hour night, then having to expend 25 percent more energy to get through it.
The use of shelterbelts and woody draws as loafing cover provides even greater energy benefits than roosting cover. Not only does a well-designed tree belt negate the energy costs of wind chill, it produces a warmer temperature inside the belt than outside the belt. With the still air inside a belt and the solar collection ability of dark-colored conifers, the temperature within a belt can be 5°F warmer than the surrounding air. In such a belt, pheasants can survive with 3 percent less energy.
The Big Spur Blog is written by Jesse Beckers, Pheasants Forever’s Regional Wildlife Biologist for North Dakota. If you have a pheasant habitat or pheasant biology question for Jesse, email him at JBeckers@pheasantsforever.org.
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