Reproductive patterns in king eiders

Abstract

Mammalian predation, avian predation, female body condition and food availability on the breeding ground are likely the main factors influencing nesting success in tundra-nesting waterfowl. These driving factors are mediated by the primary life history characteristics; incubation behavior, female body size, nesting associations, and nest site selection. I created a conceptual model illustrating how these factors are interrelated and how they impact nest success through a variety of pathways to better understand the evolution of a species' nesting strategy and patterns observed in the field. The importance of the driving factors likely varies between sites and with the species nesting strategy. Given the conceptual model, I predicted the difference in life history characteristics and nesting success at two sites that vary in any of the four driving factors. I tested the model and associated predictions using King Eider females (Somateria spectabilis) breeding on Alaska's coastal plain by comparing selective forces influencing nesting strategies at two sites, Teshekpuk and Kuparuk, between 2002 and 2006. King Eiders fit the model with some modifications to the mediating pathways. Site differences were found in many of the reproductive parameters which matched the prediction of more available forage at Kuparuk than at Teshekpuk. No differences in either avian or mammalian predation pressure were evident between sites. Eiders at Kuparuk had higher nest survival and incubation constancy than at Teshekpuk. Body mass and nest selection were similar between sites. Although questions concerning the nesting strategies of King Eider remain, I feel that this was a valid approach to identifying selective forces impacting nesting strategies and applicable to tundra nesting waterfowl in general.