The mission of the Flock app is quietly subversive: to encourage users to ditch their screens and explore the wonderful world of birding

On a brilliantly bright afternoon in his gallery and studio in Bolinas, a small town on the northern California coast, Keith Hansen was putting the finishing touches on a watercolor of an almost improbably flamboyant painted bunting.

With an ultra-fine sable brush, he made a few intricate additions to the cobalt blue plumage on the bunting’s head, and, satisfied with his work, slipped the watercolor into a stout binder that every few days welcomes a new addition.