Opuntia is used almost exclusively as structure for the construction of breeding and roosting nests. Most nests are constructed between 1 - 2.5m above the ground surface and have been observed as high as 5m above ground level. The spines of Opuntia deter numerous predators from the breeding and roosting nests cactus wrens construct in these species. During the hottest days of early summer, cactus wrens were observed by the Andersons (1973) in the shade of mesquite trees, creosote bush, and palo verde trees. The cactus wren's coloration provides protection when it is away from the nest or the roost while foraging in the shrub layer or on the ground.
Cactus wrens establish resident territories and maintain them for life. Territories are utilized for mating, nesting, brooding, and feeding and range in size from 0.5 - 2ha.
The greatest concentration of remaining habitat is, and as seen in figures 61 and 62 will continue to be, on MCB Camp Pendleton. About 10% of the region's remaining wren habitat (5,000ha) will be lost in Plans Build-Out.