This nest was located only four feet above the ground in a large live lodgepole pine. My attention was first attracted to the locality by the unusually vigorous scolding of the parent woodpeckers. A closer approach revealed the cause of the excitement.
A bear had located the nest, probably through the noise of the young woodpeckers, which were old enough to come to the nest entrance to receive food, and which squealed with anticipation of a meal any time any bird, animal or person came close to the nest tree. In an endeavor to get at the young in the nest, the bear had bitten out slabs of green wood twelve inches long, two inches wide, and one-quarter of an inch thick. The muddy stains around the inside of the nest entrance showed that the bear had thrust his nose into the hole repeatedly. But after gnawing over an area 10 by 10 inches on the tree trunk to a depth of more than an inch, the bear gave it up as a bad job. Had the nest been in an old stump, the outcome would probably have been different. This offers a reasonable explanation of the tendency of certain woodpeckers to nest in living trees.
Mr. Kennard tells in his notes of a female hummingbird that attacked one of these woodpeckers: “Several times she swooped down at the woodpecker, who, quick as a flash, would dodge around the trunk and out of her way.”
Winter.—The Arctic three-toed woodpecker is normally mainly resident in winter throughout most of its breeding range; it is a hardy bird and its food supply is available at all seasons, the grubs on which it feeds remaining in the wood for more than one season. Probably a few wander southward nearly every winter, and there have been several heavy flights of these birds into the Northeastern States, which it is not easy to explain. Dr. Josselyn Van Tyne (1926) has given a full account of one of these invasions, to which the reader is referred. Mr. Forbush (1927) writes:
It is difficult to determine exactly what causes these unusual migrations, They are not forced by inclement weather, for one at least has occurred in a mild winter. * * * It seems probable that the unusual invasions of the species into New England follow summers when its food has been unusually abundant. An excessive food supply tends to fecundity, and overbreeding naturally compels expansion and induces migration, whether among the lower animals or humankind. Since the above was written, Mr. Josselyn Van Tyne has published a paper regarding the unusual flight of this species in 1923 in which he advances a similar explanation. He says that between 1909 and 1914 there was an irruption of the spruce budworm in eastern Canada and Maine which resulted in the death of many trees and a consequent increase of bark-beetles and borers, followed by an increase in the number of these woodpeckers. On the other hand a scarcity of the usual food supply may cause migration. A wet season with few fires in the woods or a scarcity of insects (such as the spruce bud-moth) that kill trees might, later, cause a migration.
Illustrating the length of the sojourn of these woodpeckers during the winter of 1923-24, Dr. Van Tyne (1926) says:
The greatest concentration of these woodpeckers recorded at any one point was on the estate of Mr. F. H. Kennard where scores of dead and dying white pine afforded an abundance of their special food. The first one seen was a male collected on October 17. Another individual appeared by October 20 and during the winter at least three males and two females were accounted for, while all indications point toward the actual presence of perhaps twice as many. The most remarkable fact about this group of birds, however, was the length of their stay, for both males and females were seen as late as the middle of May and at least one male stayed through the early part of June and was last seen on June 12.
Other invasions are recorded by Mr. Forbush (1927) as follows: “A great irruption of these birds occurred in the autumn of 1860. During the following winter Mr. George O. Welch often saw as many as six or eight at once in a piece of fire-killed timber in Lynn. * * * In the autumn of 1925, there was a lesser movement, and many returned through New England in the spring of 1926. In the autumn of 1926 another considerable southward migration occurred.”
DISTRIBUTION
Range.—North America south to the Central United States; nonmigratory.