Botanicals. In pairs, from top:

Longleaf Mexican- or Mormon tea (Ephedra trifurca)

Desert sumac (Rhus microphylla)

Arizona walnut (Juglans major)

All photos from the San Pedro Riparian National Conservation Area, Cochise County, Arizona. Please click any photo in the set for enlarged views. 

Bullock’s oriole (Icterus bullockii), feasting on western tent caterpillars, at the 

San Pedro Riparian National Conservation Area, Cochise County, Arizona. 

The tent caterpillars—Malacosoma californicum—have thoroughly stripped this cottonwood of its recent spring growth, leaving only leaf petioles and central veins attached to the twigs. Most trees will recover after the annual caterpillar infestation and begin producing secondary leaves. But if infestations are particularly severe over consecutive years, affected trees can weaken and die.