| Abstract: | The consequences of avian egg-size variation on offspring quality and survival remain unclear. We evaluated the effects of egg-size and hatch-date variation on survival of Lesser Scaup Aythya affinis ducklings in the wild. Duckling mass at hatching increased significantly with increasing egg size. Ducklings from larger eggs survived better than those from smaller eggs. We suspect that ducklings from larger eggs survived better because of advantages associated with larger or more efficient utilization of nutrient reserves, or both. We were unable to detect any within-clutch differences in egg size of survivors and non-survivors, nor any consistent direction in the difference in egg size between survivors and nonsurvivors within clutches. This suggests that within-clutch variation may be insufficient to have survival consequences for offspring. In addition, ducklings that hatched later in the breeding season had a higher probability of survival. We suggest a food-dependent hypothesis as an explanation for the seasonally increasing survival and for later nest initiation of Lesser Scaup compared with other North American ducks. |
