The cost of birdseed has taken off. By some estimates, you’ll pay 50 percent more this year to keep the cardinals fed through the winter. Reasons for the soaring prices include the high cost of gas and the diversion of such staples as corn for new fuel technologies. Laura Erickson, author of “101 Ways to Help Birds,” explains how to keep your spending grounded.

• Don’t buy cheap mixed seeds. Mixed bags are less expensive per pound (about $13 for 20 pounds) but add weight with fillers, such as wheat and oats, that birds don’t like. To economize, buy black oil sunflower seeds. They’re nutritious and just about every seed-eating bird likes them (about $8 per 10-pound bag at Target).

• If you scatter small feed on the ground, use white millet, found at animal-feed stores or online at amazon.com ($49.97 for a 50-pound bag). Find fantastic feed and bird information at Cornell University’s ornithology lab Web site, birds.cornell.edu/AllAbout Birds, or at lauraerickson.com.

• To avoid spoilage, use a simple tray feeder. Find one at Wild Birds Unlimited (from $15.99; wbu.com). That should stop your savings from going to seed.