MODELLING THE EFFECTS OF RIVER FLOW ON POPULATION DYNAMICS OF PIPING PLOVERS (CHARADRIUS MELODUS ) AND LEAST TERNS (STERNULA ANTILLARUM ) NESTING ON THE MISSOURI RIVER

Abstract

Reservoir management on the Missouri River has changed the flow regime that once created dynamic emergent sandbar habitat (ESH) for the interior least tern (Sternula antillarum) and piping plover (Charadrius melodus). High flows that create large amounts of ESH are now rare, but the remaining interannual variability in river stage has strong effects on the amount of ESH available for nesting shorebirds. The scarcity of habitat has led the United States Army Corps of Engineers to develop an adaptive management plan for the restoration of ESH to support nesting terns and plovers. We describe the stochastic simulation models of ESH, plover populations and tern populations used in the adaptive management process, and examine the effects of river flow on projected outcomes of habitat restoration. The population models are most sensitive to uncertainty in adult survival rates. Model validation against historical amounts of ESH and population sizes suggests the model is a reasonable predictor of future dynamics. Flow variability contributes as much uncertainty as parameter estimation error to plover model projections but negligible uncertainty to the tern model. Autocorrelation in flow between years has stronger effects on population outcomes than the intensity of habitat restoration effort does. We compared population outcomes after a habitat-creating flow with population outcomes following habitat restoration and found that large pulses of habitat creation produced similar or better outcomes in the short term than low but consistent habitat restoration. However, bird populations fared better in the long term with low levels of restoration when habitat-forming flows were rare. Copyright © 2013 John Wiley & Sons, Ltd.