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Discussion of "Natural hydrograph of the Missouri River near Sioux City and the least tern and piping plover" by Donald G. Jorgensen

January 1, 2012

The author analyzed stream-flow data from a single gauging station to predict preengineering flooding frequency for "sandbar islands adjacent to stream gauge on the Missouri River at Sioux City." He predicted dates that sandbars would be exposed and discussed his results relative to reproduction by least terns (Sternula antillarum) and piping plovers (Charadrius melodus). His analysis predicted sandbar inundation during nesting and concluded that "successful migrations of age-zero juveniles leading to recruitment would not have resulted from the use of the sandbar islands for attempted reproduction most years in the Sioux City area." We argue that the author (1) overlooked published historical records of breeding terns and plovers on the Missouri River and nearby systems, (2) inaccurately portrayed inundation for Missouri River sandbars and the importance of high flows for forming sandbars, and (3) underestimated these species' ability to withstand periodic reproductive failures. We conclude that the data do not support the author's contention that the preengineered Missouri River was "unfriendly" to terns and plovers.