Different Time and Energy Budgets of Lesser Snow Geese in Rice-Prairies and Coastal Marshes in Southwest Louisiana

摘要

Many bird species use human-made habitats and an important issue is whether these are equally suitable foraging habitats as are historical, natural habitats. Historically, Lesser Snow Geese (Chen caerulescens caerulescens; hereafter Snow Geese) wintered in coastal marshes in Louisiana but began using rice-prairies within the last 60 years. Time spent feeding was used as an indicator of habitat suitability and time and energy budgets of Snow Geese were compared between rice-prairies and coastal marshes in southwest Louisiana. Composite diets of Snow Geese have a lower energy density in the rice-prairies than in coastal marshes; thus, we predicted that Snow Geese would spend relatively more time feeding in rice-praires to obtain existence energy. However, time spent feeding was higher in coastal marshes and thus, not proportional to energy density of composite diets. Snow Geese in coastal marshes ingested less apparent metabolizable energy than did Snow Geese in rice-prairies. In rice-prairies, juveniles spent more time feeding than did adults; however, time spent feeding was similar between age classes in coastal marshes. Undeveloped foraging skills probably cause juvenile Snow Geese to forage less efficiently in coastal marshes than in rice-prairies. These findings are consistent with recent trends in Snow Goose numbers, which increased in rice-prairies but remained stable in coastal marshes.