 Nests were most often built on the southern to southeastern side of the tree.Patton reports that nest trees in Arizona had crowns that were 35% to 55% of the total tree height, and most often were d.b.h.. Nests are built in trees occurring as part of a grouping of trees with interlocking crowns.Dwarf mistletoe ("Arceuthobium vaginatum") infestations that cause the formation of "witches brooms" are often incorporated into or support Abert's squirrel nests.