Egg-Laying Time and Laying Interval in the Common Eider

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. Abstract. We determined the time of day at which eggs were laid and the laying interval (time between laying of successive eggs in a clutch) in the Hudson Bay race of the Common Eider (Somateria mollissima sedentaria), at La P6rouse Bay, Churchill, Manitoba (58?24'N, 94?24'W). Nests were found at the one-egg stage and were subsequently visited three times daily. Analysis of the nest contents at each visit allowed us to estimate mean egg-laying times as well as the mean time at which eggs were lost to predators. The estimated mean egg-laying hour was 13:49 (CST, 95% CL 12:30-15:06). We detected no selective advantage to laying at this time based on the timing of egg predation. The average egg-laying interval was 27.7 + 3.4 hr. Laying intervals decreased with increasing clutch sizes. For clutches of four and five eggs, the estimated interval between the last two eggs was significantly longer than that for intervals between all other eggs, all other comparisons between intervals were not significantly different. If last-laid eggs were excluded the mean laying interval for all eggs was 26.1 + 4.3 hr, confirming that the last egg in a clutch takes longer to produce. We suggest that longer laying intervals of last-laid eggs may be related to hormonal changes associated with the onset of incubation. University of California Press and

Evidence of Population Declines among Common Eiders Breeding in the Belcher Islands, Northwest Territories

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Extended Laying Interval of Ultimate Eggs of the Eastern Bluebird

“…Although the extended interval for the ultimate egg may reflect a difficulty of making the last egg, other explanations are worth consideration. Watson et al (1993) noted the longer laying interval of ultimate eggs in the Common Eider (Somateria mollissima) and attributed the pattern to the onset of incubation causing hormonal changes that impede formation of the last egg. Specifically, rising prolactin levels may reach a point of causing the ovary to start regressing even as the last egg is traveling through the oviduct.…”

Differential investment and costs during avian incubation determined by individual quality: an experimental study of the common eider (Somateria mollissima)

“…During the 1995-99 breeding seasons the colony was visited daily from the start of egg laying in mid-May to determine the laying date and clutch size. The eider lays one egg per day (Watson et al 1993) and the clutch was assumed to be complete when no new eggs were laid over a 2-day period. The common eider produces from three to six eggs, but clutches of four and five eggs are most common Proc.…”