Nutrient Reserves Of Lesser Snow Geese During Winter And Spring Migration

I studied body composition, diet, and behavior of midcontinent lesser snow geese (Chen caerulescens caerulescens) on their major winter areas and during spring migration from January to May 1983-84. Members of this population regularly overwinter in three habitats--marshes along the Gulf of Mexico, rice fields in Texas and Louisiana contiguous to coastal marshes, and corn fields in Iowa, Missouri, and Kansas. Lesser snow geese did not store nutrient reserves that could be considered to have been for the purpose of reproduction the following spring. Differences in accessibility of foods in different winter habitats and the feeding mode required to obtain them was related to differences in bill morphology. Body size was also different among different winter habitats. Accessibility and nutrient composition of food in each of the habitats interacted with local climate to affect the body composition of geese differently in different winter habitats. Snow geese in marsh habitats appeared to be able to regulate fat reserves in response to prevailing weather. An important preadaptation of lesser snow geese was the highly labile gut morphology, which can rapidly accommodate changes in diet quality.;During spring, lesser snow geese switched to a diet of green vegetation and seeds (mostly by-product corn), and granivory eventually replaced herbivory the farther north that geese had migrated on the prairies. Both males and females stored fat and protein, but only females stored mineral reserves. There were consistent patterns between the sexes and between years of study in the timing of nutrient accumulation. Rates of protein and mineral storage were highest during early migration. Fat storage was related to vernal equinox, and most fat reserves were stored in the northern prairies. As fat was accumulated, it became increasingly related to body size, attaining a maximum in southern Manitoba. After snow geese left the prairies, a second episode of protein storage, but no fat storage, occurred on southern Hudson Bay. Drought on the prairies was related to reduced body protein when geese were in southern Manitoba, but snow geese were able to store enough protein on coastal Hudson Bay to erase any between-year differences in body protein on the prairies