AMERICAN MAGPIE 137 



an owl flew up it was followed closely by a magpie. In the vicinity each 

 owl nest was situated close to an occupied magpie nest. The owls did 

 practically all their foraging at night when the magpies probably slept, 

 and hence they most likely needed some special protection just as might 

 be provided by the thorny canopy over the nest. This was near the 

 nest-leaving time for both species. 



The black-billed magpie nests sometimes in tall trees, but oftener in 

 tall bushes, especially in thorny ones. In trees the nests are placed often 

 on low horizontal limbs sometimes close to the trunk and nearly always 

 less than 25 feet from the ground. In bushes the nest may be in the 

 extreme top, and nearly always it is far enough above ground to be out 

 of reach of large foraging mammals. 



Preference for certain kinds of bushes or trees to hold the nest seems 

 to depend largely on what ones are available in each locality. In various 

 places the following kinds of plants have been recorded as providing 

 sites for nests of black-billed magpies: Alder, aspen, birch, buffaloberry, 

 Cottonwood, fir, hawthorn, juniper, pine, scrub oak, and willow. 



Both birds of a pair take an active part in nest-building; both carry 

 materials and place them on the nest. However, one of the pair, prob- 

 ably the female, gives more attention to the actual shaping of the nest. 



In some localities magpies regularly use the same nests year after 

 year. In this case the old nest is repaired and new material is added 

 to it. Sometimes a remarkably large structure is thus built. In other 

 localities the birds seem never to use a nest for a second brood but 

 always build an entirely new one or, at most, build upon an old one, 

 using it mainly as a base. Repair of nests is not limited to reoccupation. 

 The birds see to it that the nest is kept in repair during the incubation 

 and brooding of the young. If a part of the canopy is torn away, it 

 is likely to be replaced quickly. 



The use of magpies' nests by other birds has been discussed fully by 

 Rockwell (1909). The abandoned nests furnish protection during severe 

 rain or hail storms, or other severe weather, for robins, blackbirds, 

 bluebirds, warblers, and other species that live along the timbered 

 streams. Some birds, the horned owl, long-eared owl, and screech owl, 

 make use of these nests almost continuously for daytime hiding retreats. 

 These birds, especially the first two, also lay their eggs in old magpie 

 nests. The sparrow hawk uses these nests for laying, but nearly always 

 it chooses nests that still have their roofs intact. Rockwell noted that 

 sparrow hawks that utilized old magpie nests always appeared timider 

 than the ones that nested in cavities of trees. Other species reported 

 as using these nests for their eggs or as bases for nests of their own 

 are the sharp-shinned hawk, at Fort Lewis, Colo., the mourning dove. 



