Red-breasted Nuthatches are uncommon in our area. However, we've been fortunate to have one spend the winter a couple of times. Nuthatches are the only birds that move headfirst down the trunks of trees. They are searching for beetles, insects and insect larvae in cracks and crevices.
From the beginning of nest building until the young leave the nest, Nuthatches use their beaks to take drops of pitch or resin from conifers and smear it around the entrance of their nesting hole. Ornithologists believe this is an "atavistic" trait which, according to Merriam-Webster is a trait or character typical of an ancestral form and usually due to genetic recombination. The entrance ends up with two inches or more of sticky pitch around the hole. Other nuthatches fill cracks and crevices next to the entrance hole with bits of fur. This is an interesting trait as we know of no other bird that caulks around the entrance hole of their nesting cavities.