Egg Characteristics and Body Reserves of Neonate Ross' and Lesser Snow Geese

Abstract

We studied the effects of species, nesting chronology and egg size on composition of eggs and goslings of Ross' (Chen rossii) and Lesser Snow Geese (Chen caerulescens). Compared to early nesters, late-nesting Ross' Geese laid eggs with less yolk protein, which in turn produced goslings with smaller pectoralis muscles. Larger pectoralis muscles of young that hatch early may enhance thermogenesis when conditions are colder. Egg composition varied isometrically with egg size. Conspecifics from larger eggs were structurally smaller for their egg size yet contained the same relative nutrient content as goslings from smaller eggs ; thus goslings from larger eggs had relatively more lipid reserve. Larger egg size may give an initial energetic advantage to goslings during periods of nutritional or thermal stress. Although no interspecific 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 skeletal tissue mass than did Snow Geese which indicates greater functional maturity of Ross' Goose neonate tissue. Digestive efficiency, thermoregulatory ability and locomotor capacity may be relatively better in Ross' Geese than in Snow Geese and these characteristics may represent adaptations to metabolic constraints associated with smaller neonate body size and forage requirements.