About noon on 20 July 1974 I saw an immature Least Tern (Sterna albifrons) at the northeastern corner of the Cottonwood Reservoir along U. S. Highway 89 about four miles north of Wilsall, Park County, Montana. I observed the bird in bright sunlight through a 20X scope for about 20 minutes, often as close as 50 feet. The length and wing-span were no more than twice those of two brown-backed swallows (probably Rough-winged Swallows, Stelgidopteryx ruficollis) that twice harassed the tern closely.