Tree cavities are formed by tree disease and decay and by woodpeckers. All six woodpecker species in Alaska excavate cavities for nesting and roosting. Most other cavity_nesting birds use abandoned woodpecker holes. Usually a pair of woodpeckers excavates a new hole every year. Before selecting a final nest site, a pair may start, then abandon, several holes. During fall, overwintering woodpeckers also excavate cavities for winter roosting. However, woodpeckers are only able to excavate holes in dead or decaying trees.
Once you begin feeding birds in the fall, you have make a commitment. A feeder often attracts more birds to an area than natural food sources can support. Thus, if you stop feeding them, the birds might not be able to find enough food to survive. So, if you plan a vacation, be sure to have someone restock you feeder regularly while you are gone. Species we should be careful NOT to attract include bears and moose.