Behavior, energetics and management of refuging waterfowl: a simulation model

A stochastic simulation model, designed to test the effects of alternative management schemes on refuging waterfowl populations, was constructed from data on fall-migrating lesser snow geese (Chen c. caerulescens) at the DeSoto National Wildlife Refuge, Iowa. Components of the model include goose population level, food density and distribution, food-searching flight characteristics, feeding rates, activity and energy budgets, migration rates, and the effects of weather, hunting pressure, and land management practices on the system. Independent data were collected to test the model's validity. The model validly describes movement from the refuge core to distant feeding areas, and it provides insight into factors affecting emigration. Refuge population level was not sensitive to shifts (?20%) in the input values of 25 selected parameters, but hunting mortality and daily foraging distances were sensitive to several combinations of parameter perturbations. Model outcome was most sensitive to changes in digestive efficiency, mean food density, and the proportion of refuge fields in which food was available. In other model experiments, increased hunting pressure caused significant (P < 0.05) increases in hunting mortality and a reduction in the refuge population. The direct effect of hunting was less important in reducing waterfowl population size than the associated disturbance of feeding geese by hunters, which reduced energy gains and subsequently hastened emigration. Geese in the vicinity of the DeSoto Refuge feed almost exclusively on waste corn. Simulated hunting mortality increased significantly (P < 0.0001) when waste-corn density was moderately reduced because increased goose movement resulted in more shooting opportunities for hunters, but, at extremely low levels of food density, refuge use by waterfowl declined and hunting mortality was reduced. When superabundant food was provided on the refuge, hunting mortality was reduced and waterfowl use of the refuge increased. An artificial reduction in size of the feeding arena, from a radius of 121 km to 8 km, did not affect waterfowl population levels because food supplies were adequate within 8 km of the refuge core. The model can be used to simulate the effects of other management scenarios and is a valuable tool for identifying and meeting management objectives. WILDL. MONOGR. 96, 1-35 Journal Paper J-11908 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Project 2427. 2 Present Address: Department of Biological Sciences, Eastern Kentucky University, Richmond, KY 40475. 3 Supported jointly by the U.S. Fish and Wildlife Service, Iowa Conservation Commission, Iowa State University, and Wildlife Management Institute. This content downloaded from 157.55.39.35 on Wed, 31 Aug 2016 04:14:15 UTC All use subject to http://about.jstor.org/terms