The Timing and Energetic Consequences of Egg Formation in the Adelie Penguin

To study the timing of egg formation in the Adelie Penguin (Pygoscelis adeliue), we gave 150 females an oral dose of Sudan black dye before they laid their eggs. This lipophilic dye is incorporated into yolk synthesized on the day of dosing and deposited on the developing ovum as a blue layer. First, second, and third fresh eggs laid by dosed birds were collected. Analysis of the timing of egg formation revealed that rapid yolk deposition (RYD) on the first ovum began 10-l 2 days prior to cessation of feeding. Second and third yolks were initiated sequentially at 3-day intervals. The total time necessary for RYD was 14-17 days, and was followed by a 5- to 7-day lag period between yolk completion and laying. In total, 19-24 days were required to produce each egg. Within clutches, second and third eggs were smaller than the first egg, owing to reduced albumen content, while yolk mass remained relatively constant. We determined the daily energy, protein, and lipid input into a clutch and estimated that the use of a female’s body reserves during a 12-day fast requires 307 g of muscle tissue. Of this, approximately 123 g of muscle (40%) are required to produce the 24 g of protein contained in egg components deposited during the fast. Both the long lag period and the 3-day interval between laying eggs may be adaptive in reducing the daily protein demand for egg production.