Original article

• Main Author: Gregory J. Robertson
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1997
• Subjects: Churchill; Common Eider; Somateria mollissima
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.457.7642; http://www.sfu.ca/biology/wildberg/papers/RobertsonBES98.pdf

Abstract Hypotheses regarding the evolution and maintenance of intraspecific nest parasitism were tested with data collected during a 3-year study of common eiders (Somateria mollissima) breeding near Churchill, Manitoba. The nest parasitism rate was highest (42.4 % of nests) during the year with the highest nest density and the best environmental conditions, and lowest (20.2 % of nests) in the year with the lowest nest density and the poorest environmental conditions. Over the nesting season, parasitic eggs were laid at the same time as normally laid eggs. Most parasitic eggs (>75%) were laid before the host female laid her third egg. The majority of the parasitic eggs were the first or second egg produced by the parasitic female. When a parasitic egg was laid before or on the same day as the host female initiated her clutch, the probability of her first egg being depredated before incubation was sig-nificantly lowered. First- and second-laid eggs suered a high rate of predation probably because nesting fe-males do not attend their clutch until their second or third egg is laid. Hypotheses that some females use intraspecific nest parasitism to parasitize the parental care of other females were inconsistent with these data. Egg adoption is a likely explanation for the prevalence of females incubating parasitic eggs in this population. Key words Common eider á Somateria mollissima á Intraspecific nest parasitism á Brood amalgamation á Alternative reproductive behaviours