Migration chronology and multi-scale habitat selection of wintering midcontinent greater white-fronted geese

Abstract

Food resources are assumed to limit waterfowl populations in the Mississippi Alluvial Valley, thus bioenergetic models are used for spatial allocation of food resources to provide adequate energy to support regional waterfowl population objectives. Changes in population abundance and distributions of midcontinent greater white-fronted geese Anser albifrons have implications for region-specific conservation planning of energetic resources for wintering waterfowl. This research aimed to quantify timing of arrival of greater white-fronted geese to wintering areas and quantify foraging behaviors. These data can help refine bioenergetics models and facilitate future waterfowl habitat planning efforts in the region. Bioenergetics models account for energetic demands of wintering geese by assuming they forage in flooded habitats 25% of the time across a 110-day winter planning period. Although this assumption has gone untested, our estimate of time spent foraging in flooded habitats (27.4% ± 5.8%) confirms the current model parameter of 25% of the time. However, we suggest that this is not the best parameter to use in bioenergetics models as greater white-fronted geese in our study foraged in dry habitats (72.6% ± 5.8%) more often than in flooded habitats. In addition, selection for rice fields in heavily weighted toward early winter (November; β = 2.85), and use declined 70% as winter progressed (February; β = 0.89), likely due to depletion of available rice grain, hunting pressure, and the physiological need to switch from a greater carbohydrate diet to a nitrogen-rich diet. In addition, white-fronted geese arrived to wintering areas earlier than current models accounted for with a mean arrival date of 30 October (± 2.5 days) to the Mississippi Alluvial Valley. We suggest early arrival to the wintering area and greater selection for dry rice fields during early winter indicates exploitative competition by white-fronted geese for shared food resources that may not be adequately accounted for in current bioenergetics models. We suggest current models underestimated energetic demands and the competitive nature of early migratory greater white-fronted geese.