High Mountain Lakes Provide a Seasonal Niche for Migrant American Dippers

Abstract

Abstract We studied summer use of high elevation lakes by American Dippers (Cinclus mexicanus) in the Trinity Alps Wilderness, California by conducting repeated point-count surveys at 16 study lakes coupled with a 5-year detailed survey of all available aquatic habitats in a single basin. We observed American Dippers during 36% of the point-count surveys and found birds at 10 of 16 study lakes. Over 90% of the American Dipper sightings were in lentic habitats in Deep Creek Basin. Bird presence at a lake was positively correlated with steep rocky littoral zones and high densities of caddisfly (Trichoptera) larvae. We also observed numerous successful foraging bouts on juvenile life stages of lentic-breeding amphibians. We did not find any nests at the lakes but did observe juvenile dippers. American Dippers are highly adapted to flowing waters, and our findings coupled with incidental observations from the literature and other researchers suggests that high elevation lentic waterbodies have been largely ov...