The most popular item on our bird-feeder menu today is suet. We have a log (five inches by six feet) tied to the trunk of a tree in the backyard. One-inch holes drilled into the log are stuffed with suet.
Visitors to that dining hall by midday Tuesday included Downy, Hairy, and Red-bellied woodpeckers, chickadees, and two Brown Creepers. Birds were there frequently. Blue Jays, American Crows, and nuthatches also eat suet.
Small birds maintain high body temperatures, and, being small, they lose heat faster than larger animals. It's a surface to volume issue. Small birds must produce more body heat than large birds to offset loss of body heat.
For the next two days, on any cold day, the best food you can offer is suet.