Egg-Size Variation in the Imperial Cormorant: On the Importance of Individual Effects

[摘要] Abstract. Although some of the components of egg-size variation in birds have been studied, there is a lack of approaches in which phenotypic variation is both partitioned and its causes are analyzed. We partitioned and analyzed the phenotypic variation in egg size in 1588 eggs from 572 clutches of the Imperial Cormorant (Phalacrocorax atriceps) over three breeding seasons (2004–2006) at Punta León, Argentina. We estimated repeatability and phenotypic plasticity of egg size, investigating the effects of year, date of laying, body size, and body condition on egg-size variation within and between clutches. Egg size varied widely, the largest egg being >2× as heavy as the smallest. The repeatabilities of both egg size and mean egg size (0.761 and 0.894, respectively) are among the highest reported for any bird. Most variation among clutches was due to differences among individuals, being weakly related to date of laying and unrelated to year, body size, or body condition. Egg size decreased with the egg's or...

[学科分类] 动物科学

[关键词] inter- and intra-clutch egg size variation;maternal effects;Phalacrocorax atriceps;phenotypic plasticity;repeatability;seabirds