But if you want to see big changes in the number of birds in your yard, Saffier said, simply plant a bird-friendly garden.
"You can change the dynamic of your backyard with just a plant or two. A person who puts in a bird garden will see almost-instant results," he said.
Birds require food - seeds and fruit - and water for drinking and grooming. And they need shelter - formal, as in birdhouses, and informal, as in plantings and underbrush, for nesting and for protection against the elements and predators.
When it comes to laying out the welcome mat for birds, gardeners can hang a sack of nesting materials, such as straw, string, dog hair or cotton, and put out sand or crushed eggshells to provide the grit that birds need to help them crush their food. A heated birdbath in winter, when other sources of water are frozen, is a nice touch, too.
Garden catalogs are full of whimsical items that add interest to the winter garden and help sustain birds: wreaths and birdhouses made of seeds; metal cattails and mesh balls that hold seed or suet. Catalogs also carry high-tech devices that let you listen to bird conversations from a distance.
And, during the winter, garden centers seek to draw in paying customers by offering workshops and lectures on how to garden for wildlife.
"People are destroying a lot of the habitat through development and the paving of roads," said Kress, author of the Audubon Society Guide to Attracting Birds. "What we have an opportunity to do on our properties is replace some of that. It isn't the same as a mature forest habitat, but many kinds of birds can adapt, and some of those are declining species."
Saffier trains volunteers to help homeowners create a more bird-friendly backyard, and he isn't surprised that most of them are gardeners, who already have a store of knowledge on plants, shrubs and trees.
"I get more garden people than bird people," he said. "When we look at all the people we are trying to reach, the low-hanging fruit, as it were, are the gardeners because they already have an affinity for the natural world."
Perhaps the most difficult lesson to teach is this: Be a lazy gardener.
"That's our motto," Saffier said. "Stop cleaning up."
Leave the seed heads instead of cutting back all the perennials; they provide food. Leave the leaf piles; they shelter insects and larva, Leave the ornamental grasses; they provide shelter.
