106 BULLETIN 17 4, UNITED STATES NATIONAL MUSEUM 



observed it below the pines. I have taken incubating birds in June 

 m the Cuyamaca Mountains at altitudes of about 7,000 feet. The 

 nesting sites here were in very large dead pine trees and inaccessible." 



This woodpecker seems to show a tendency to nest, at least occasion- 

 ally, at greater heights above ground than its northern relative, but 

 otherwise its habits seem to be very similar. 



The eggs are similar to those of the northern race. The measure- 

 ments of 20 eggs average 24.67 by 18.60 millimeters ; the eggs showing 

 the four extremes measure 26.70 by 19.50, 25.60 by 19.70, and 22.62 

 by 16.67 millimeters. 



PICOIDES ARCTICUS (Swainson) 

 ARCTIC THREE-TOED WOODPECKER 



Plates 15, 16 



HABITS 



Although not found in the strictly Arctic, treeless regions, this bird 

 is probably well named, for its range as a whole averages farther north 

 than that of any other woodpecker except P. tridactylus. It is a bird 

 of the boreal forests of spruces and firs, ranging as far north in 

 Alaska and northern Canada as these trees grow, and extending its 

 range southward throughout the Canadian Zone into the Northern 

 United States and farther southward in some of the higher mountain 

 ranges. 



In the eastern portion of its range this woodpecker seems to prefer 

 the dense virgin forests of spruces and balsam fir, but it nests mainly 

 in the more open windfalls or burned-over clearings where there are 

 plenty of dead, standing trees in which to excavate its nest. In New 

 York State, near the southern limit of its breeding range, a typical 

 locality is thus described by Laurence Achilles (1906) : "At three 

 thousand feet or more above the sea, in the denser spruce and balsam 

 forests of the Adirondacks, the Arctic three-toed woodpecker is fairly 

 common. * * * 



"The trees near the nest were chiefly spruces, with a few balsams and 

 birches scattered among them. The birds had selected a rather open 

 place for their nesting-site, as, within a radius of ten yards from 

 their nest, there were several windfalls and dead spruces. The ground 

 was carpeted with moss, while linnea, clintonia, wood-sorrel and 

 bunchberry were blossoming in profusion near the base of the tree." 



In the Midwestern States and Provinces, the Arctic three-toed shows 

 a decided preference for tamarack swamps, especially where these 

 have been burned over, leaving a few dead or dying trees still stand- 

 ing; these trees not only furnish an abundant food supply but offer 

 many convenient nesting sites. Into such attractive habitats these birds 

 sometimes congregate to form small breeding colonies. 



