Some of the birds here in the Sonoran Desert are a bit difficult to see unless they are moving because they are the color of their usual environment. This coloration is an adaptive form of camouflage, and it provides them some protection against predation. Of course, this form of color camouflage works best with predators that have good color vision, such as other birds.
Curve-billed Thrashers (Toxostoma curvirostre) are similar in color to much of our desert dirt here in Tucson (excluding the few areas with reddish volcanic soil).
Curve-billed Thrashers are usually found on the ground searching for insects and spiders or perched low to the ground with the pale brown of the desert as a background, making them occasionally difficult to spot.
I will sometimes feel like I am being watched when I'm outside and not see anything until the beady-eyed Curve-billed Thrasher moves, or I spot its characteristic, curve-billed silhouette.
Unlike Curve-billed Thrashers, hummingbirds are rarely found on the ground, unless they are injured. Instead, hummingbirds are often found hovering near the green leaves of flowering plants as they feed on flower nectar.
Most of the hummingbirds here in North America, such as this male Broad-billed Hummingbird (Cynanthus latirostris), have iridescent green backs that blend in quite well with the average green color of leaves.