That makes them welcome in most gardens, as they scarf up caterpillars and flying insects. Some, such as hummingbirds, are pollinators. Niger thistle seed doesn't germinate, and it attracts small birds such as finches. More important than putting seed out is to plant natives that either feed birds directly or provide shelter and nesting sites. Native plants do the best job of providing food and shelter for our native birds.
Many species are dependent on the habitat provided by native vegetation.
Taken all together, home plantings can aid the bird population in our area. The most obvious predator in suburban areas is the common housecat. At least equip your cat with a bell and consider keeping it indoors during the spring breeding season. Spay or neuter your cat, and call the humane society if you have feral cats living nearby. Limit the poisons you use in the garden.