By Amy Geiszler -Jones

Backyard birdfeeders are a great way for people to enjoy watching birds. And on top of enjoying the appearance of a bright red cardinal outside your window during the dull, gray winter weather, you can feel good about helping feathered creatures find food.

Feeding birds is a popular hobby in the United States, with more than 52 million people feeding wild birds, according to a national U.S. Fish and Wildlife survey conducted by the Census Bureau. More than a half-million Kansans provide food to birds, that same survey found.

WSU avian biologist Chris Rogers has been studying the impact of providing supplemental food to birds and their buildup of fat to survive the winter. Studying winter survival strategies has become a leading field in behavioral ecology.

"Because fat has costs and benefits, we’re learning how birds balance those costs and benefits to maximize their chances of survival," says Rogers, an assistant professor in biological sciences, of his longtime research. "The study of winter fat strategies is the study of winter survival strategies."

For the past two winters, Rogers has done his research in Kansas, comparing the body fat content of birds – primarily sparrows, finches, chickadees, titmice and woodpeckers – that get supplemental feed and those that forage on their own in the wild. He’s also studied birds in Iowa, British Columbia, Washington, Michigan, Indiana, Tennessee, Kentucky and Wisconsin.

Birds build up fat reserves in the winter for two reasons: to maintain a high body temperature overnight and to provide an emergency energy reserve at dawn in case snow or ice has covered up any food sources. Starvation and being killed by predators are the primary causes of death for birds in the winter.

What Rogers is trying to find is what happens to birds when you feed them: Will they continue to forage for their own food to build up fat because they perceive a risk or will they think their chances of starving are slim because food is supplied?

While there are two models of thought – one predicting birds increase their fat with supplemental food and the other predicting a decrease, it’s ornithologists like Rogers who are doing the research to determine which one is more likely. Rogers hasn’t come to any conclusions yet, but he thinks supplemental food will help increase a bird’s body fat.

Starting in December until early March, Rogers, helped by four student assistants, hauls more than 200 pounds of birdseed every three to four days to feeding areas at WSU’s Ninnescah Experimental Tract, a 330-acre field station in southwest Sedgwick County near Viola.

Rogers is comparing the body fat of birds feeding in that area to birds feeding in three other tracts of natural habitat in Sedgwick and Butler counties. To ensure none of those birds foraging on their own were "cheating" by visiting nearby birdfeeders, he and his assistants captured and colorbanded 285 birds in that area during the past two winters. When they observed nearly a thousand visitations by birds at those feeders, they didn’t spot any with the brightly colored leg bands.

"No birds thought to exist on natural food only are sneaking to feeders and using private birdfeeders," Rogers says.

To capture birds at all four sites, he and/or the field assistants raised fine nylon nets measuring about 40 feet long and 8 1/2 feet high. They checked the nets every 30 minutes, pulling the birds that are caught in the net and measuring their body fat.

Because birds deposit their fat equally in two areas on their bodies, you can’t use the pinch test like you would on humans, where fat is deposited in one continuous, even sheath under the skin. Birds deposit their fat reserves in the furcular depression, more commonly known as the wishbone area, and in an area between their breast, right above their legs, to maintain their center of gravity while flying.

Rogers’ work is not without its low points. He often battles inclement weather to make regular visits to both the supplemental and natural feeding areas. It has some comic points, as well, like the time he forgot he had left a captured cardinal in his field jacket when he went to a restaurant. The bird flew out of his pocket and started hopping around the restaurant’s salad bar, looking for food.

Because of his longtime work with cold-weather birds, Rogers was invited to make a presentation at a major, international bird conference hosted by the Smithsonian Institute earlier this month. He presented a theoretical paper, proposing that adaptive fat regulation of temperate-zone birds could also be observed in tropical birds.