When I was in my pre-teens, a brother of mine assembled a bird-house for House Wrens. I had not seen or even heard of the House Wren (or any other wren) and figured it was a total waste of time. That year, I learned that wrens did indeed visit and live on our Iowa farm. I also found out that they are great at hiding but can sing loudly.
Since moving to Colorado in June, I have seen three species of wrens. All are quite loud and are very good at hiding.
The first wren I discovered was the Bewick’s wren. I heard it from the front steps of my apartment on my first weekend here. Several weeks later, I saw an adult moving through the vegetation near my steps with fledglings in tow, feeding them.
My second wren was the Rock Wren. I wouldn’t call this bird secretive. It usually sings loudly from a conspicuous perch.
The third wren was the Canyon Wren and the one I was most looking forward to seeing again. It is heard more often than it is seen. It has a loud booming voice. They can cling to vertical rock walls.
By reading the habitat descriptions of the three wrens above, you should be able to get a feel for the type of landscape in and around the Colorado National Monument; dry, sparsely vegetated, rocky canyonlands.