Incubation Behavior of Spectacled Eiders on the Yukon-Kuskokwim Delta, Alaska

Abstract

We studied incubation behavior of Spectacled Eiders (Somateria fischeri) on the Yukon-Kus kokwim Delta in 1996. We trapped 19 females on their nests and weighed them in early incubation and again at hatch. Average daily weight loss for incubating females was 16.6 ± 1.0 g day -1 , which resulted in a cumulative loss of 26% of body weight throughout in cubation. Nest attendance was monitored for a portion of the incubation period using tcmperature sensing artificial eggs. Incubation constancy averaged 90 ± 1%. Avcrage rccess lcngth was 37.1 ± 0.9 min, and nests cooled an average of 4.2 ± 0.1°C during recesses. Recess frequency averaged 2.5 ± 0.1 recesses day - 1 , and most reccsses (70%) occurred between 10:00 and 22: 00. Incubation constancy varied among females, but was not related to changes in body weight or incubation period. There was no influence of ambient temperature on incubation recess length, however most recesses were takcn during the warmest part of the day. We found considerable variation among females in patterns of daily incubation constancy, nest cooling, recess frequency, and recess length. It is not clear from our results what factors constrain incubation behavior of Spectacled Eiders, but we suggest that individual females respond to a complex suite of variables.