Logs Used as Nest Sites by the American Dipper

During spring and summer 2024 I followed activities at an American Dipper (Cinclus mexicanus) nest built in an exposed site on the end of a horizontal log overhanging Rattlesnake Creek, Missoula County, Montana—the first log reported as a dipper nest site on this creek, which has been the focus of prior studies of the American Dipper’s breeding biology. Logs are rarely reported as nest sites in interior western North America (∼1% of 452 dipper nests) but are used more frequently near the coast (∼13% of 319 nests); use of logs also varies among sites within the coastal region. Reasons for regional differences in log use are not clear but could include the abundance of logs in surveyed streams, specific attributes of available logs or log jams, the availability of other nest substrates, and differences in the sizes of dipper territories, which could preclude occupancy of otherwise suitable nest sites.