Temporary flightlessness as a potential cost of reproduction in pre‐laying Common Eiders Somateria mollissima

• Published in: Ibis
• Main Authors: GUILLEMETTE, MAGELLA, OUELLET, JEAN‐FRANÇOIS
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2005
• Subjects: Somateria mollissima
• Online Access: http://dx.doi.org/10.1111/j.1474-919x.2005.00402.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1474-919x.2005.00402.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1474-919x.2005.00402.x

The rapid growth and reabsorption of the avian ovary is thought to be adaptive, as it reduces predation risk and the metabolic cost of flight. In this paper, we use an extreme case of parental investment to show how the survival of gravid birds may be impaired by reduced take‐off ability. In still air, temporary flightlessness is regularly observed in female Common Eiders Somateria mollissima preparing for breeding. From a sample of pre‐laying females collected in the Baltic Sea, we quantified the relationships among body reserves, organ mass and take‐off ability using a general model of take‐off performance. Average body mass at the beginning and end of follicular growth was, respectively, 32% and 43% higher than winter body mass. Wing‐loading increased significantly during ovary development whereas the relative mass of flight muscles decreased. In contrast, organ mass and somatic body mass were constant from early follicular growth until laying, indicating that the observed increase in body mass was caused by ovary growth. The average specific lift production of individuals collected at the beginning of follicular growth was 9.7 N/kg, which is similar to the lift required to become airborne (9.8 N/kg). As ovary mass increased, lift production decreased to 9.2 N/kg at the onset of laying. These results indicate that temporary flightlessness results from the accumulation of large body reserves and subsequent ovarian growth. Predators of Common Eiders are diverse and may come from air, water and land. We suggest that temporary flightlessness may decrease adult survival through predation, and may represent an important cost of reproduction.