Winter World_ The Ingenuity of Animal Survival - Bernd Heinrich [29]
By late afternoon the snow was coming down so thick that it almost blinded me. I passed the old hemlock tree with a honeybee nest that I’d found by lining bees the previous fall. A hollow ash tree where I had once seen a raccoon hole up in January stood near, but hearing the loud kek-kek-kek of a pileated woodpecker, I veered toward a huge dead elm instead. These woodpeckers had for several years in succession carved out their nest cavities in this tree. I saw three cavities, one above the other and spaced about four to five feet apart. Woodpeckers go to great trouble and effort to always make a new nest cavity each spring. There is then a yearly progression of fresh empty apartments for flying squirrels, crested flycatchers, barred owls, and potentially bats.
When I reached the woodpecker-made nest holes, I again heard the pileated’s kek-kek-kek-kek, reverberating through the woods, and then I saw the big gorgeous black bird. White wing-bars flashing, it sliced through the storm and landed on the far side of a sugar maple near me. It jerked its white-striped head with flaming red crest toward me from behind the shielding tree. I backed off, and the bird then flew to the elm and entered one of the old nest holes, possibly one of its own used for nesting in a previous spring.
Woodpecker holes are used by other birds for shelter in the winter as well. I have often found red-breasted nuthatches overnighting during the winter in old downy or hairy woodpecker holes, and the pygmy nuthatch (Sitta pygmaea), which often travels in small flocks, overnights during the winter in tree holes with its many companions for added warmth (Knorr 1957; Guntert, Hay, and Balda 1988), as do Carolina chickadees (Pitts 1976) and occasionally also bluebirds (Frazier and Nolan 1959).
It is one thing to find existing shelter and make use of it; it is quite another to expend time and energy making a shelter for future use. Surprisingly, some other northern woodpeckers do just that. In late November and early December when temperatures are dropping rapidly and the first snowstorms blanket the woods, I often hear steady tapping unlike a woodpecker’s more intermittent rapping for food excavation. Following the sounds to a decaying tree or thick tree limb, I find the ground and/or snow below littered with small light-colored wood chips. The head of a downy or a hairy woodpecker invariably appears at a round hole, then shakes to release a billful of shavings, and quickly tucks back in to resume hammering. At first I thought these birds were confused, perhaps by misreading the photoperiod—the hours of daylight versus dark that many animals use to keep track of the seasons—to begin nesting a half year early. However, the finished holes excavated in the late fall or winter (in more decayed wood than nest holes) were invariably used by the birds that made them for overnighting sites; I flushed out the bird in the evening by tapping the tree, but it quickly reentered the hole to spend the night there. (Woodpeckers use no nesting material beyond a layer of dry wood chips, but the nest cavities provide obvious protection from the cold.)
Since it may take a pileated woodpecker or a sapsucker up to two weeks to hammer out a cavity in a tree whose interior is softened by fungus, one wonders why other winter birds don’t build “regular” nests for shelter since such nests can be built in several days. For example, a pair of golden-crowned kinglets constructs its well-insulated nest of moss held together by spiderwebs in just