Cliff Swallows
Driving along highway 88 in California, I noticed a large flock of birds darting in and out of a large conglomerate of rock along the Carson river. I pulled over and scrambled down to the river’s edge. From a distance it doesn’t look like much but zoomed in I was able to get a photo of the numerous nests of Cliff Swallows built into the rock wall. 
Snapshots by Kats 