EGG CHARACTERISTICS AND BODY RESERVES OF NEONATE ROSS AND LESSER SNOWGEESE

We studied the effects of species, nesting chronology and egg size on composition of eggs and goslings of Ross' (Chen rossii) and Lesser Sno w Geese (Chen caerulescens). Compared to early nesters, late-nesting R oss' Geese laid eggs with less yolk protein, which in turn produced go slings with smaller pectoralis muscles. Larger pectoralis muscles of y oung that hatch early may enhance thermogenesis when conditions are co lder. Egg composition varied isometrically with egg size. Conspecifics from larger eggs were structurally smaller for their egg size yet con tained the same relative nutrient content as goslings from smaller egg s; thus goslings from larger eggs had relatively more lipid reserve. L arger egg size may give an initial energetic advantage to goslings dur ing periods of nutritional or thermal stress. Although no interspecifi c variation in egg composition was observed, Ross' Geese hatched with more protein (scaled to egg size) and larger gizzards (scaled to body size). In addition, Ross' Geese had less water per gram of dry skeleta l tissue mass than did Snow Geese which indicates greater functional m aturity of Ross' Goose neonate tissue. Digestive efficiency, thermoreg ulatory ability and locomotor capacity may be relatively better in Ros s' Geese than in Snow Geese and these characteristics may represent ad aptations to metabolic constraints associated with smaller neonate bod y size and forage requirements.