Upside Down Tree?

On my morning walk I took a detour off the lake path and went into another lake neighborhood. I found this strange looking tree at one of the houses. I know it's been there for years, but just never noticed it before. It doesn't always have leaves on it. It is a Boojum Tree (Idria columnaris) and it is related to the Ocotillo.This one is is about 18 feet tall, and I found out it is about 20 years old. These things can get as tall as 70-80 feet! It is a deciduous stem succulent tree is native to the Baja California area of Mexico. The San Diego Zoo Wild Animal Park has a large collection of them, and the U of A has three that were planted in the 1920's. The Desert Botanical Garden also has one that is about 25 feet tall. The flowers are a tubular shape and pale yellow. They are borne on 16 inch panicles if the tree is over six feet tall. They sell for about $1000.00 per foot. Small ones are available at local cactus and succulent nurseries.

Near the top of the tree is an unidentified bird's nest. Not a great photo but that's what that brown patch is....