For the Birds: Which Seeds Are Best?
Though feeding wild birds is one of the nation’s most popular hobbies, few studies have been conducted on avian nutritional needs; here are some of the most recent findings
AS THE WEATHER TURNS cooler, it’s time for backyard birders to start cleaning out feeders and stocking up on supplies for winter feeding. Trying to decide which bird seed to buy? Surprisingly, the answer is not clear-cut. Despite our enthusiasm for backyard feeding—more than 50 million people feed wild birds in the United States alone—very little science has gone into understanding the nutritional needs of wild birds or even which seeds they like to eat.
According to David Horn, associate professor of ecology at Millikin University and a leading expert on the subject, “wild bird feeding is one of our most understudied wildlife management issues.” To promote smarter decisions about bird seeds and how to feed wild birds, he recently established the National Bird-Feeding Society (www.birdfeeding.org). Many of the group’s recommendations will be based on Project Wildbird, a 2005–2008 study led by Horn in which several thousand volunteers contributed observations from their backyard feeders. Among the study’s results are that black oil sunflower, white proso millet, nyjer (thistle) seed and sunflower chips are the most highly sought after seeds for reasons that are only now being researched (see www.projectwildbird.org).
To stay healthy, birds must consume a mix of fats, proteins, carbohydrates and various vitamins and minerals to fuel a metabolism that can require up to a whopping 10,000 calories a day (equivalent to a human consuming 155,000 calories). A bird’s inner furnace burns especially hot during flight and the breeding season and on the coldest days, which means the animals must make highly efficient choices about what they eat.
A backyard feeder is an especially efficient place to forage because it mimics what scientists call a “resource patch,” a cluster of food much like a fruit-laden apple tree. But although a feeder offers an abundance of food, evolutionary pressures encourage birds to continuously sample a wide variety of foods because any bird that becomes dependent on a single patch or type of food will perish if it runs out.
This means you don’t have to worry that birds will become overly dependent on your feeder. Indeed, in a classic study of black-capped chickadees, ecologist Margaret Clark Brittingham of the University of Wisconsin found that even when they have access to unlimited feeder food, these voracious seedeaters obtain 79 percent of their daily energy needs from a variety of wild sources. Birds are remarkably proficient at assessing potential food items for nutritional content and quality. If you watch your feeder closely, you may observe the animals lightly rattling individual seeds in their bills to weigh and taste them before deciding whether to drop them to the ground or eat them. Low-quality foods are discarded and a consistently low-quality food patch may be avoided for a while—a behavior called “neophibia” that explains why birds learn to avoid your feeder if you put out old, moldy or inedible seeds.
At the University of California–Davis, animal nutrition expert Kirk Klasing is studying how birds taste and assess the nutritional profiles of foods. He recently discovered that the animals “mostly taste umami,” referring to the Japanese term for one of the five basic tastes, in this case a taste for protein. This benefits birds, says Klasing, because seeds high in protein are nearly always high in fat, and fat provides the energy boost that gets a bird through cold winter nights or the energetically demanding needs of flight. It’s possible that birds may taste the fat content of seeds as well.
Project Wildbird also found that favored seeds tend to be high in protein and fat. In addition, studies have revealed that birds choose seeds that are easily handled and digested (like millet), emphasizing that for birds, eating is not only about nutrition but about consuming a lot of food very quickly while avoiding predators. Research has shown that given a choice between high-quality, cumbersome seeds or low-quality, easily handled seeds, birds consistently choose the latter.
Whichever seeds you buy, a growing body of evidence shows that backyard feeding helps wild birds—the animals’ growth rates, survival rates, breeding success and clutch sizes all improve markedly when they have access to feeders. Putting out high-quality seeds, bought as fresh as possible and stored in a dry clean place, seems to offer seed-eating birds the best of all worlds: highly nutritious food that is also easily processed. And in the depths of winter, when a bird’s food needs may increase up to 20-fold, that is nothing to turn your beak up at.
California naturalist David Lukas wrote about junco sex appeal in the February/March 2009 issue.
Learn More About Bird Feeding
NWF’s Certified Wildlife Habitat® program provides homeowners with all the information they need to create quality outdoor spaces for birds and other wildlife using native plants as well as feeders. To learn how you can receive certification and attract wild creatures to your property, visit www.nwf.org/gardenforwildlife.