There are many bird nests in the cliffs of the Oldman River. Usually under an overhang keeping them dry and protected. The are interesting pieces of architecture made by small birds. After talking to Ken at the Helen Shuler Nature Center in Lethbridge I leaned that they are most likely Cliff Swallow nests. It looks like they are empty at the moment waiting for the tenants to return.
Walk with me
(Without leaving the couch.)