Nutrient Reserves and Reproductive Performance of Female Lesser Snow Geese

We studied the relation between nutrient reserves and reproductive performance of female Lesser Snow Geese (Chen caerulescens caerulescens) in 1971 and 1972 at the McConnell River (6050'N, 9425'W), Northwest Territories, Canada.We determined the potential clutch size of a pre-laying female by counting large (>20 mm), highly vascularized ovarian follicles; actual clutch size of post-laying females was the number of post-ovulatory follicles.Females with larger nutrient reserves had, on average, larger potential clutches.Reserves were used by the geese during laying and, after laying, the mean weights of reserves from females that laid different size clutches were not significantly different.We suggest that clutch size in Lesser Snow Geese is determined by size of nutrient reserves.Successful females used much of their remaining fat and protein reserves during incubation but this use was not significantly modified by the size of clutch they incubated.Late in incubation some females depleted their reserves and left their nests to feed; others starved to death.Thus, to reproduce successfully a female must retain, after egglaying, sufficient nutrient reserves for her own maintenance during incubation.