What’s This? No. 18 should be self-evident. The winner of this challenge, however, will name the species that left its mark on this rock (which I suspect is Shinumo quartzite). I photographed this on Phantom Creek in Grand Canyon National Park on March 4, 2014. For extra credit name the other “dropping” in this image.

Added March 17: We have a winner! 


Well, we have many winners. But Mark Council was first to identify this as the footprints and droppings of American Dipper. Mark’s answer came in to the blog a mere three minutes before our second-place winner, Sue Cloutier, who is the Ken Jennings of What’s This? Also check out some of the more creative answers in the comments below.

American Dipper is our only aquatic songbird; those footprints do indeed suggest the feet of a “perching bird” (in the order Passeriformes) rather than webbed feet. Dippers nest along streams across the western US and Canada. Water does truly roll off this bird’s back; it swims and walks underwater on stream beds, where it feeds on aquatic insects. Meanwhile, the eco-astute Audrey Clark noted the Fremont cottonwood (Populus fremontii) leaf on the boulder, which also helps with scale in this image, and the yellowish duckweed gathered in the eddy.

Find the entire suite of What’s This? challenges here.