At first glance you may think that these cholla plants are filled with dead bits that are decaying. Not at all! Those many shaggy clumps that you see are all birds' nests. This cacti is particularly great as a nest location because it is quite unwelcoming to any would-be predators. An encounter with a cholla thorn is very painful indeed.
I'm a transplanted New Yorker who loves the Tucson climate. On New Year's Day I have a bit of fun calling my (snowbound) east coast friends to announce that I'm drinking coffee while sitting on my patio. (: