Embryonic Development and Nest Attentiveness of Wood Ducks during Egg Laying

Waterfowl often begin incubation during egg laying, thus creating developmental asynchrony within clutches. We investigated levels of intraclutch developmental asynchrony (IDA) during early incubation within naturally incubated clutches of Wood Ducks (Aix sponsa) in South Carolina. IDA averaged 2.2 ± 1.0 SD days (n = 59) during a 2-year study. A higher average level of IDA in 1988 corresponded with larger average clutch size during that year. Date of nesting did not affect levels of IDA, but larger clutches had increased levels of IDA. In 1988, reduced hatching success was observed in clutches with greater than 3 days of developmental asynchrony, suggesting a cost associated with the early initiation of incubation while still laying eggs. Nest attendance data collected during the later stages of egg laying indicated that females spent approximately 50% of the day at the nest. Female Wood Ducks engaged in nocturnal nest attendance during egg laying thereby allowing time to meet the nutrient demands of egg synthesis during the diurnal period.